Use the financial gain bit to convince stores to treat them properly. If people see them in halfway decent tanks (at LEAST 1 gallon, if they will not go larger) with filters, decoration, and heaters, they will assume that is what they need to be properly cared for. That means they will BUY larger tanks with all the furnishings, which means more profit for the stores.
I walk into my LFS, and if I knew NOTHING about bettas, I would think that anything less than 1 gallon with a bit of decoration, filtration, and heaters was not enough. Ideally they would be in more, sure, but they get cleaned constantly, so they always look nice and healthy. Sure, once in a while you get one that has something wrong, but considering the number of bettas (and fish in general) they have, seeing one or two in all the tanks is not that bad. Most are swimming around, flaring at each other, building bubble nests, and just being bettas.
Also, if the fish look healthy, they are going to be brighter, more likely to flare, etc. That means they are going to be more likely to be SOLD.