I like Wesley's idea of including a caresheet of the most important details and a link to here (and to the detailed Red-Eyed care sheet). Seems like an easy thing for a store to do yet I've almost never seen it done.

As a bonus, you could also include (or sell) baby photos of their frogs. People love baby photos of their pets. You can have a picture of a bunch of eggs with an arrow pointing to one. Hah. Or of their parents, or siblings, etc.

There are reptile/amphibian shows you can go to for an increased customer base if you want to sell directly. Toronto has a big one twice a year (and Mississauga apparently, and coming to Kitchener) Ontario Reptile & Exotic Pet Expo and there is a smaller one in the Waterloo area whose name I forget, though it is mostly geckos and snakes (I went to the last one). They probably have vendor fees though, so it might not be worth it. You could probably try selling photos and frog art as well as frogs. Just an idea.