Avoid buying snaps at hardware stores for $3.50 as they likely dont have a stainless spring and will begin to stick almost immediatly.
Come on...if something is cheaper and works just as well, if not better, then go for it. Dive shops are incredibly overpriced for things like this, and there's no reason to just throw your money at them, expecially when they can't even tell you where it came from/what sort of spring it has.
Tom