Try www.connects2.com as this seems quite a comprehensive list. They are easy to fit as long as you can get the radio out. Halfords was the cheapest when I got one for a Toyota and they will fit them as well.
You can get an FM transmitter which plus into the cigar lighter and takes a line in from your mp3 player. Your radio then picks up the FM signal and you can play your mp3s through your car stereo. They are under a tenner and work fine also they are not illegal ( I checked that one out ). Try typing 'fm transmitter' into the e_bay search engine and you will see what I am on about. You can hard wire a connection in but the transmitter is so simple and saves any hassle.