I'm not sure how pristine of a 20 year old track-only car you're going to find, but...
Places to check:
1. Bring A Trailer, although the prices go up and not down and most of the people making comments are just haters.
2. Wire Wheel in Vero Beach, FL, although the prices are reportedly a tick high.
3. On Facebook, look for a Corvette guy named Brian Bowers in either NC or SC; he fully restored one with his dad, and there are tons of build photos. It's not a GTS, but it has a DOM chassis and is legal for a W2W logbook. I think he needs to paint a couple of body parts, though (some post-restoration tire wall contact).
4. I know of a guy in the Tampa area who is considering selling his GTS, although he's a bit high on his price. Let me know if you want me to put you in touch with him. The car was turning laps at Sebring last season; so, it should still be turnkey.
Mark