I had a friend actually brought the RCA connection cable and cut them to bare wire and connected to the wire behind the car stereo it worked good, or you can use a fm modulator, but this will not give you a clean sound quality all that, still works.
also most of the RCA Jack is made of speaker wire, if you know what your doing you could just make one your self, radio shake is the place you want to go and pick things up from there make everything your own. Be-sure to twisted the wires together to make a stronger connection. Good luck.