Online is always a really good way to get a really healthy specimen, but I purchased mine at petsmart. You are 100 precent right when you say they keep there amphibians and reptiles in a really small cage. The one I purchased was sharing a 10 gallon tank with 3 adult whites tree frogs. However, I bought him and he is still alive today, 2 years after the purchase.

If you can, ask one of the employees to see them feed. If they seem to have interest in food, they are healthy specimens. However, these frogs don't always have an initial response to food, especially after they have recently been fed. So, if the frog appears too skinny, or has bumps or cuts on it, or is a different color than it should be, then do not purchase it.

Good luck with your frogs