Retrofit USB port to stock headunit

[Z750]

Ok my car has a clarion double din head unit with 6CD changer that can play mp3s. Is it possible to retrofit a port so that the mp3s can be from a thumb drive instead of CD? Anyone done it before?

 

Maybe something like this:

http://www.gromaudio.com/store/usb_adapter..._interface.html

http://yatour.en.made-in-china.com/product...ce-Adapter.html

 

I am aware of FM transmitter and AUX in options, but both do not support my steering wheel controls.