In my experience the little mom-and-pop petstores are far more likely to donate than the big chains. The chains have certain charities that they already support and pretty much blow off new requests.
Many US-based reptile rescues use Petfinder.com as their link to each other in helping to place animals. I don't personally use the service because most of the animals I take are short-term rehabs that will be going back to their owners after their post-operative care is done but I do help folks who need to rehome animals get set up with Petfinder.
The Zombie Mama is here!