no clue about any other place than the BMW dealer.
There are only a select few places that sell this other than BMW itself, the reason is that this part is actually produced exclusively for BMW instead of being just a bosch/hell/ZKW/Motometer/ect part. You might just have to go to the dealer.
Bavauto sold them when I got mine, but with my club discount it costs the same from either them or the dealer. Almost $70