Yes there are many different types of aftermarket changers that can be controlled by your radio. They are called FM modulator's. Basically you turn your stereo to a designated FM (blank) station then control your changer with supplied remote. Some even let you use your own controls, depends on how much you want to spend.
Check this out....not sure they have the best deals but it'll give you some idea...actually the prices aren't too bad.
Online car audio rainshdw
