I'm not sure if he does Hourglass Tree Frogs or not, but he does breed Clowns, and it would be worth while to check out Mike Novy's site, Rainforest Junky's - Home.
I received excellent service and some great frogs from Mike, it'd be worth it to get in touch with him and see if he has or will have Hourglass Tree Frogs available. Good luck in your search.