I did the same thing on mine automatic. Here's what I used and it works. I bought it from madvet.com, sorry Patrick I know they aren't a supporting vendor, the part is $50 plus shipping. I love the thing and it was extremely easy to install.
At last, you can purchase that manual C5 aftermarket shift knob you've had your eye on, thanks to the Shift Knob Adapter! This upgrade kit allows you to install any custom manual shift knob on your automatic C5 and keep your stock leather boot intact. Full instructions provided for an easy installation.