http://www.circuitcity.com/ssm/Audio...oductDetail.do has a good description of an item like what I'm talking about.
http://www.amazon.com/Audiovox-FM-Mo...7645269&sr=8-6 has it for a decent price.
You turn it on and it overrides the FM station for whatever frequency you choose. Then turn it off again to listen to the radio.