If you just want one for basic antenna orientation and giving you a general signal strength, (not channel specific), you can get the $39.99 one from Antennas Direct. Combined with your TV Fool report preinted out, (or brought up on a laptop, whatever), you can get a pretty good idea of what channels are stronger than the others. (usually good enough).

If you want specific dBm readings, and channel selection, you're going to be paying some decent money, but you'll have a top notch tool. If you want to go this route, I reccomend the DigiairPro ATSC tuner for $359. Unless you're going to be installing antennas regularly or servicing them, it's probably not a nessecary purchase.