I can't tell you where to find good suppliers, but I can tell you to avoid Big Box Stores. They sell inferior products, seconds, blems, and no name junk. Unfortunately, in the plumbing industry many plumbing supply houses will only sell to licensed plumbers. It is not the same as in the auto parts business where they will give pros a better price, but the general public can at least buy from them. I would suggest you look through the Yellow Pages and find shops that specialize in plumbing products then check to see if they will sell to the public. I'm sure there are some around, you just have to look.