I recommend FAB Breakers too - Article in >>
last months Total BMW magazine shows the heavily rolled 850CSi they have! apparently it's only the 2nd one they've ever had!
I was also going to suggest using an aftermarket alarm system in case
you can't locate a genuine BMW part/system or if it's turns out to be incompatible
I think North America does get BMW Car, Total BMW and Performance BMW magazines, speak to your local Barnes & Noble - as on my semi frequent US trips I have seen them on the shelves - and check out all the rest of the classifieds in case other suppliers have the part you need.
Hope this helps
Dennis! West London UK!