I'm after one myself, but bmw discontinued them in 2012. There's a guy on here from mainland Europe who makes them, but they're about 400 euros delivered. His name is Alphaflight.
I brought one from Ebay from a seller in the States called Custom Tuning, here's a link:
http://www.ebay.co.uk/itm/171276925841?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
It turned up quickly, no duty to pay. Fitting was easy with double sided tape, although you cans ee it around the edge so I am going to put in a bead of black sealant.
I will try to take some pictures of the quality which was impressive with a deep gloss lacquer, for the price: £130 delivered !!!
