Gotta thank whoever it was on this site who told me about those "Lite And E-Z" harnesses for iguanas! GOt one for my Iggy (and a matching lead), and it works great! He can't get out of it, and it must be comfortable because he doesn't even try to.
Anyway, thanks again! I love the site. If anyone else is looking for an iguana harness that actually works, I recommend these guys: