A bit of confusion here I believe...
The black stand off posts are considered part of the door panel and cannot be bought separately. However, the white pegs that are on the top of the black posts can be easily purchased (about $.50 apiece) from the dealer or from any of the usual online sources (getbmwparts.com, pelicanparts.com, etc....
Here's the part # 51411973500
Just looked up the part at Pelicanparts... $.25 here;
http://www.pelicanparts.com/cgi-bin/...C%20Each%20%20