Is it possible to add an aux input on an GM radio?

Basically my Aztek has a button thats saids cd/aux yet I cannot find an AUX input anywhere on the damn thing. This is a 2003 which basically has the same GM radio that every other Pontiac came with at the time. I'm trying to hook my Zune to it so I can listen to MP3's without having to go after market (trying to spend as little money as possible) but before I pull out the radio I was going to see if anyone knew if it had an AUX input on the back. If not is it possible to somehow add an AUX input to the radio? And before anyone ask yes I have tried used an FM transmitter and the SQ is about the same as a man slapping himself in the ass with a straw broom.

There are adapters that plug in where the CD changer would. Here's an example:
http://www.crutchfield.com/p_469GM12AX2/Precision-Interface-Electronics-GM12-AUXv2.html?tp=422

You may need to enter your vehicle info to ensure you have the correct model adapter for your vehicle.

I am looking for the same thing for my 2002 Camaro with Monsoon system. I checked the Crutchfield site and it states that this adapter is not compatible with the 02 Camaro Monsoon system.

Any other suggestions out there?

Read this, you might be able to do it.

http://ls1tech.com/forums/stereo-electronics/890811-mp3-player-into-oem-monsoon-head-unit.html

Thanks for the link. I tried searching for someting like this but didn't find this thread. Looks like the GM9-AUX will work. I go get one and try it out!