Most of the time roof rails (00 Daytona, 01 Special Edition, and 02 40th Anniversary) are on national backorder. A lot of the vendors stopped carrying them due to that. There was a small re-release of them from GM earlier this year that most didn't know about, but I haven't checked to see if any are still lurking around out there. You can generally find the left side (I believe). I know Reptile still has a few sets. I sold the couple dozen I had except the sets for my 99 and 00.
Part numbers:
Right Side 12336036
Left Side 12336037
You can always get creative with your searches on car-parts.com, search ebay and classifieds, gmpartsdirect, Pace Performance, or your local dealership. I stopped getting them once I went back to school, but you'd be surprised where you'll find them (back warehouses, salvage yards that don't know what they are, body shops, and so on).
Good luck on your search!