How short do you really want to go? Once you get shorter than a #0, you're going to look completely bald so it might be cheaper and easier just to shave with a blade.
If you really want a clippers that cuts super short, try the Wahl Balding Clippers. They cut, I think to a #00000 or #000000 -- about as close as you can go without shaving. You have to be careful you don't pinch your scalp with them, though, because they do cut really close.