I actually frequented a couple of smaller, independent pet shops down in the Twin Cities (Minneapolis/St. Paul) that specialized in small animals, such as rodents as well as reptiles and amphibians, as well as a shop that was mostly aquaria but also had some herps. They all had fabulous knowledge, great habitats and even provided basic herp vet services and medications. I have no idea if they're still in business, but it's an example of people who are really passionate and knowledgable about the animals and making sure they go to the right homes. I had gotten my ill-fated goldfish from them, who contracted Ich (potentially from contaminated water) and died when I was snowed in and unable to get medication. Hence why I'm trying to take a proactive approach and keep emergency supplies on hand for pets from now on. But they did their best trying to help me over the phone, and even offered to refund me my money or give me new fish, along with the meds. I was too upset to replace them, so I didn't go through with it. One of the employees was actually willing to drive the treatment over if the weather wasn't so bad!
The research you do can bring up rare jewels, especially when you research through state and local groups. But it is true that finding a good, responsible pet supplier is like looking for a needle in a haystack. Buying potentially ill-fated animals from pet stores may give them a better chance (or at least some happiness), but you're also supporting that pet store and proving that they have a source of demand and will continue to sell those sickly animals. If you consider yourself responsible, you'll only buy from responsible dealers and breeders (or at least take responsibility for those sickly animals and be fine if they die, though you should raise hell). Otherwise you're just part of the problem.