Welcome to DC Dave. That’s one I haven’t seen discussed on the site but that doesn’t mean it hasn’t been. Maybe some of our C5 guys will have an answer for you. You may have to buy a radio out of a salvage yard to get that knob. Then you will have a spare in case yours goes bad. Just a thought. Well anyway hope someone here has an answer for you.
If the knob looks the same as the other but doesn't fit, if the hole on the knob it too small, then try to remove some material to make it fit. If the hole on the knob is too big, try some trimmed toothpicks and use superglue to affix. Just a suggestion.
this radio is all over the place, as is this problem, so you might find the button in a junkyard gm product. I doubt anyone would sell one off a radio, so a corvette specific junkyard might not be productive, but they might know of a solution. I would suspect you would have to find one in a gm car deemed not worth breaking up, where you pick a part from a car. or perhaps a long established radio install shop would know of a solution.
I would try calling an electronics repair shop to get a feel about what is possible. ,perhaps an old one might have a collection of just in case spare bits from the past , or perhaps they could order one new, as a replacement part. I have read the radio was built by pioneer, but am unsure. I have a couple of Panasonic cd trays for the changer is why I say that, but know the trays were standardized within the industry . I also think the knob might have been kind of generic, a lot of radios back then used the same type of small control, and perhaps the same knob.
with luck, you might find a friend who could print you one. this was the answer that a lot of people searching for a knob for the heads up display slider found, a little bit of plastic held in place with spring tension , that apparently liked to shoot off into the land of the lost. so many people had the same complaint, that someone put up a digital file for the knob, so that people could take it to a maker space, and a few hobbyists corvette owners volunteered to print the part for free. perhaps if the word got out, one of those guys would print a copy of a knob
shortly after the hards up file went public, I bought a reproduction knob for about five bucks from southern car parts, including the tension steel.
depending on where your interests lay, the part could be easily fabricated provided a suitable plastic rod could be found, perhaps at a hobby shop. wood fabrication and paint could be a temporary filler until a better solution could be found, with the obvious difficulty being not splitting the material when making the hole. heat shrink tubing might help with any splitting or durability problem. of course, there are lots of ways to cast small items, resin casting is very popular, but that would involve double work, in that one would first have to fabricate the mold for the piece, instead of just the piece.
if a hobby shop doesn't have a suitable rod to fabricate from, you might check into plastic clay, and just free form the shape, bake and then do some finish sanding. I used to know a woman who made beautiful little harlequin dolls, shaping the heads from a white claylike material that air hardened and seemed very durable.
I wish I had a real solution, instead of just possibilities. But with such a small part , the old saying , where there is a will , there is a way, might be applicable. It least you are not trying to build a raft to escape a desert island.
I really am unsure if you are just kidding around, suggesting the solution is buying and installing a new radio because of a missing knob is kind of like the old joke about buying a new car because the ash trays were full on the old one. I have to admit, sometimes I don't get the jokes that others find obvious .
I once put a very nice system into an old jag, I was a lot younger and have always had music and Hi fi as a hobby, but , in time I regretted cutting the walnut dash. Even though the cut was minor, and the system integrated nicely, I decided never to cut a dashboard again, as it might effect the cars ability to survive the crusher some day. plus it reflects on one's ability to steward the machine while in your care.
Others consider the usual approach that cars are a disposable commodity. I guess I have enjoyed viewing too many old cars to not try to support my particular corvette into an unknown future , even though my car is not a show car, and a C5 will never be especially collectable .
Besides, in my case , my home stereo is where my interests lay, so my investment is better served tending to my primary listening system, and just letting the car alone, as it came stock from the factory, or with easily reversible mods for the next owner. of the two paths available to any car, restore to a modern standard, or restore as stock, I choose to go the stock route , without hesitation, because everything gets dated in the passage of time anyway, I don't do track days, and the stock design satisfies my simple needs very well.
in this case it just seems wasteful to landfill a working radio , buy aftermarket stuff, adapt and install it, all because overcoming such a dinky problem as a missing knob is beyond ones ability or interest, so just throw money at the problem . personally, I would rather buy a used car with only a missing a knob or two, than one with a modified dash and a dated aftermarket radio, even though it updates the interior nicely.
I might note that the usual solution, installing a Two din video screen head unit ,gives a god result, but will require slight fabrication work, as would making a knob. But I was just offering possibilities , I don't really think replacing a knob will require more than the time to find one, there are so many out there, because the radio was installed in various lines over multiple years.
if calling an electronic repair shop doesn't pan out, I would return to investigating for old car parts. Pontiac is an orphan car line, so getting spare bits there might be easier than just inquiring only about corvette parts. I know the Grand Prix had all the high end stuff, plus more. Olds ran the same basic stuff, but any GM line with little interest , such as the econo stuff, might prove productive to investigate.
Modern units fit in with no modifications and can be reversed. Plus Bluetooth, IOS,Android touch screen back up camera the list goes on. Who mentioned throwing the stock radio away? Keep it, might come across a knob or sale to someone who’s radio gives up. On top of that they would have the knob on theirs to replace it with. Hypothetically if the car was still in production GM wouldn’t sell you a knob you would have to purchase the entire head unit. Better luck next time.