Not my field, but just asked the question for another vehicle - the local Radio Shack has a CD player with a small transmitter that transmits on the FM band. Tune your FM radio to 1 of 4 different frequencies and put the CD player under the passenger seat (or anywhere your passenger can access it easily). Power from cigar lighter.
Jon.
Good carburetion is fuelish hot air Owner, The Carburetor Shop LLC