Pot
Well, my first suggestion would be to get a hold of an ohm meter, and see what the value of the original part was, that way, you know you're money.
Just by guess though, you want a 5 or 10 ohm, with many turns. That way it's very adjustable. More than likely you'll only use a few ohms, but with a 5 or 10, you know you have plenty, and with 5+ turns, you should be able to dial it in without a problem.
If you can't find one like that at radio shack (which wouldn't surprise me, a 10ohm pot is not a normal thing), then check out digikey.
Hope it works out for you.