I see 144 copies listed as available for trade on Board Game Geek. Of course, there’s also 1500+ wishlist requests, so arranging a trade may not be easy. Still a place to start.
You are aware that GTG has been shuttered by its owners, Flat River Group, right? All new production is on indefinite hold, so stuff is just going to get rarer and rarer as time goes by.
Oh, and welcome aboard the forum, for whatever that’s worth. Good luck on your game hunt.