I lucked out with the PetLand near me. One of the guys who works in the fish department is very knowledgeable, and tries his best to care for the fish while he's there. His main specialty seems to be Koi and plants, but he's really good about other fish too.
He does have a Betta set up at home. A 5 gallon I think. He said Bettas do much better in larger tanks than the Zen Garden tanks that are frequently sold at the store.
I also second a letter to the Store Manager. If not the Store Manager, perhaps the General Manager. It's always good to list where you get the information from too, that way people can look it up if they wish, and gives your letter a little more weight.
30 US Gallon Tank: 3 Goldfish (1 White Ryukin "Salt", 1 Bronze Oranda "Pyropus", 1 Silver Oranda "Argentum")
10 US Gallon Tank: Borealis the Betta, Assassin Snail, Various numbers of Pond Snails
4 Cats (Fenris, Tatum, 'Spoo and Samantha)
Part-Time University Student
Part-Time Hospital Employee
Not enough time in the day...