Well, there's always
http://www.tirerack.com and
http://www.tires.com -- which are the big two. Outside of that, I can't help much.
What I'd do is go to a site like
http://www.cardomain.com and look at some of the GTOs on there. Find a wheel design you like, then shop the heck out of it.
I wound up digging around and found a nice 5 spoke from Boyd Coddington. They can do all kinds of things, like powder coating, as they're built to order. You might want to look into that. Good luck.