I'd try Craigslist if you haven't already. I was poking around for 4th gen interior bits today and noticed a LOT of 3rd gen part outs.
z28.com doesn't get as much traffic as other sites. I would try LS1tech or camaro source, but you might have better luck with LS1tech.
You might have to try broad keywords on craigslist, as I was finding 3rd generation part outs by searching for 1997 z28....
Good luck, if I find something I'll let you know.