aux input on a lexus

I have a 2003 Lexus IS300 with a factory 6disc cd changer radio with a tape deck below radio.I looked for an aux. input module with no luck, the radio is RDS but does not have a SAT or AUX. button. what can I use besides an fm modulator to hook up a dvd/xm/ or sirius radio to this oem radio to get a clear sound?thanks.

If there's no SAT/AUX button and it's a 6disc changer, I didn't think there was another way!  I thought that you could only go the FM modulated route!  But i would'nt doubt if there is another way!!