I've this issue too, I know the post is a few years old, but I'm surprised more people don't havethis issue!
Anyway the adapter is a 900-200.
It goes onto a 14 way connector on the head of the circuitboard inside the MIC.
Unfortuneatly they are isn'tmuch info about them, and Bosch are useless, because aparantly a company of that size only has one, and they don't sell them any more, and appear to ignoring me as I asked for a pinout/circuit diag to make one.
I'm sure it's noting more than an adapter.....
If anyone has one, please help!
Thanks