Lemurs are very cute and becoming very popular in captivity. I can see what you mean re: crazy frog lol - it's those googly eyes that do it for me. Certainly one of my favorite hylids however and as said, you can't beat a nice, plump (grumpy) sauvagii.

With regards to availability, I'm not very clear on the US or CA market. I do know that Understory Enterprises based in CA run a Captive program for the Costa Rican variety of Lemur frog. In the UK, these frogs are quite rare as they have not been bred in large numbers due to their decline and critically endangered status.

Further resources:

Understory Enterprises: Hylomantis lemur | Understory Enterprises
Project Lemur Frog: Project Lemur Frog
C.R.A.R.C: Costa Rican Amphibian Research Center | Research and Conservation of Costa Rican Amphibians

Best James.M ACITP