The eBay guys are by far the best source. They've got some pretty cutting-edge parts for cheap!
Be aware of your focusing needs, and that tighter focus raises the mcd number but that doesn't necessarily mean it emits more light overall. Tight focus is a problem for displays meant to be seen from any angle. The unusual "strawhat" domed-top is a 140 deg spread. The "inverted cone" type is a side-emitter, which is particularly good for lights planted inside a diffuser, like patio lights.
Decide whether you want common anode or common cathode. Generally, common anode is significantly simpler to drive.