I agree with Leticia H. When we couldn't find a part for a discontinued faucet, Emigh's suggested Brothers. This is a contractor's warehouse store that also sells to the public. It's not "pretty" except they do have good display sections. But if they don't have it, they can tell you if and how you can get what you need. And my favorite, they have a clearance section at the front door! Definitely worth checking them out.
PROS: Staff will pursue a search for an obscure item--nice guys.