RealOEM shows part # 51248402195, at BMW of Fairfax you can get it around $51 each, plus $9 shipping. I tried to save on shipping once and went to pick my order up, but then i thought, I'd rather ship, save on the traffic aggravation... lol...

I am not sure about aftermarket options...

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E53 X5 4.6iS
147K mi - Sold May 2013
Tireprints left in:
USA, Nicaragua, Costa Rica, Panama, Russia

E53 X5 4.8iS built 2005-10-17
66200 mi - June 2012
96000 mi - June 2013
112000 mi - June 2014
OEM fire extinguisher
OE first aid kit
OE tow hitch
OE TV module
OE aspheric mirror
K&N air filter
black/white badges
rear camera
4-channel video recorder

Here is the list of things I have done to the X