We have a member who had an extra one he was willing to part with. I had pm'd him a few months ago and still had it. Found him through a search for this part, but dealer ended up replacing it under warranty on the second go around. Let me see if I can dig up the thread.

Here you go. Last post on this thread. Never asked his price.
http://www.xoutpost.com/bmw-sav-forums/x5-e53-forum/63406-my-7-yrs-old-son-ruin-blind-windows.html