a quick google search revealed the following
(which wasnt much info)
http://www.circlebmw.com/parts/electronic/rearview.htm

another option is to smack one of these on there and some how connect it to the nav screen and make it turn on when car is put into reverse http://www.autoanything.com/generic_...9764&p_id=2316



The truth is I wanted a backup camera on my audi and was even going to install one (with a small lcd display mounted on the sunvisor (flipped down to see camera) but after I realized the cost involved and the reason for me needing a backup camera (dont know why people need a camera in the front) which was to not bump anyone while backing up......I realize the park distance sensors can work just as well..... let me know if you find something though...i'd be interested in what it looks like...