It looks like you need Part Number 5 on this diagram:- https://www.realoem.com/bmw/enUS/showparts?id=DU92-EUR-10-2006-E86-BMW-Z4_M32&diagId=61_1619#61316940989
Sopers of Lincoln or Cotswold BMW offer a forum discount, otherwise it's a breaker like Quarry Motors if you want it for less!
You'll also need to ask "srhutch" to make up the section of wiring loom to connect it.
Apologies if you already knew all that!