Try calling some beef processors in your area. They often sell beef that producers bring in for slaughter, and you can ask for exactly what you want. But you don't have any control over the quality of the beef and can't see it before purchase.
Personally I like the beef back ribs. Yea, they don't have a lot of meat, and may seem not worth the effort to cook, but it's hard to find something much tastier to gnaw on.
Short ribs are traditionally from the short plate (hence its name), but ribs from the chuck can also be marketed as short ribs. If you can get some of the plate short ribs not cut (sometimes called dinosaur type ribs), they're the best.
The problem with beef ribs is that they can have a considerable amount of fat, and the better cuts go to higher end bbq restaurants. Costco and Sam's are you best bet for retail cuts.