I know that this thread is getting a little old, but I have luck with this quite often.
Most of the brands that major part stores carry have downloadable online catalogs (ie, gates, goodyear, dorman, BWD, Timken, BCA, sealed power, pioneer,...., etc)
If you hunt down the part number that you need and call the parts store with it, you would be supprised how often you can get what you need.
If a counterperson glances at the computer screen, tells you they can't get it, and never gets the catalog off the shelf, try this method. A lot of times they'll have what you need on the shelf.