Additionally, if you go to the manufacturer's website, they often have a link somewhere on the part's page that will list known distributor stock. This will show you which distributors have that particular part, and how many they have. It's not 100% accurate as it's not necessarily updated in real time, but should be within a day or so. I've found it to be a big timesaver when looking for oddball stuff in that it can save you the trouble of having to look everywhere as it at least gives you a feel for who doesn't have it...
-Pat