I get my Muriatic Acid, CYA and occasionally a couple gallons of 12.5% Chlorine at my local independent pool store. All the items at way better prices than the chain store. I've also been known to come home with an inflatable pool toy every other trip, which is about 3-4 times a season!
I would never say to not go to a pool store, but don't go their blindly, without being able to refute the garbage they sometimes spew. Best example would be like sending my 62 year old mom to Jiffy Lube.... sharks in the water.