As Jeff W says, McMaster Carr is an outstanding source. Also McMaster Carr's So Cal distribution facility is in Santa Fe Springs. I don't think they have store at that location, but you can buy online or over the phone. The item should arrive next day.

Another source is Grainger Industrial Supply. They do have stores you can shop at, but I don't think the stores stock every item offered in the catalog, but can probably get the item relatively quick. http://www.grainger.com/Grainger/wwg/start.shtml

Good luck!