Retro fit USB to standard CD Player

Hi All,

Has anyone ever retro fitted a USB port that acts as a CD Changer whilst still retaining the Aux input?

I know some Leon PFL have the USB connection under the seat as optional extra

And the face lift have the AUX/USB near the cupholder in the center

I am not looking at a cheap eBay option

I am looking to retain the original stereo or do a facelift stereo converation onto Pre face lift

Hope someone can shed some light on this

or even the correct necessary loom to make a USB connection as i know it will require few pins in the quadlock connector