I think I’m an amateur, and your best bet is to pop one out and take it to the parts counter.
But if I had to wager, I’d go with 61 13 8 377 072.
You’ll notice two #15s (universal socket housing uncoded) on the list at:
http://www.realoem.com/bmw/showparts...11&hg=63&fg=30
My thinking is that the non-festoon style socket would be the less expensive of the two.