For calipers I would look at some of the classifieds on this site (as well as the other corvette sites) or call a salvage yard, you are going to pay a lot for new calipers at a dealer- if you have to have new check out GMpartsdirect.com they usually have good prices.
For the caliper you might want to post this in the C5 parts for sale section of this and other forums.
Try NAPA for the rotors. I just bought a set and fortunately the seller was close enough to me that I was able to pick them up. If you have to have them shipped they'll cost a fortune, they are very heavy.
got my c5 calipers and baskets new from the local acdelco parts store, bunch cheaper than the local dealer as the dealer discounts are tiny...some dealers will give better discounts than others, apparently it's up to them.