I just (1/2 hour ago) bought a pair of 15-2104 remotes at Radio Shack at the clearence price of $9.97 each. That store still had 4 more.

If your local Radio Shack has any at that price, that is the best choice available for a bargain RS/OFA remote. It does do advanced codes. It has a real nasty recessed P key, so doing a lot of advanced code testing without a JP1 cable would get quite annoying. If you already know the codes, that wouldn't be an issue. If you don't know the codes, get a JP1 cable rather than try to struggle without it.