The home improvement stores near me sell fittings from companies like Spears and Lasco, so it's the same stuff you're going to get anywhere else. I've used lots of this stuff with no problems.
I know Im stating the obvious but you're talking about PVC fittings right? Assuming yes I agree with wolfman. Its the same stuff you get anywhere else. If you know any plumbers see if you can buddy up to them and use their account at the local plumbing supply place.
I just finished a DIY KalkReactor, and I found the highest quality fittings, and best prices at a local pool supply house. They even carry clear schedule 40 PVC for $13 a foot. That's cheaper than anyplace I've ever heard.