[StLouisCPhT]

There was a device mentioned over in the mylink upgrade thread someplace that could potentially do what you need. I think it primarily was for HDMI mirroring, but it might also be able to handle multiple video ins.

Edit: https://www.carid.com/2011-chevy-cr...xxess-backup-camera-interfaces-464365804.html

This could be what you are looking for. Must be really new, never seen it anywhere before. Not even directly through the Axxess/Metra website.