I just ordered one for my sedan from a BMW service center. They scanned my key to assure the car was prewired and to verify the parts needed. I believe the e90 and e92 use the same parts.
The Sirius Radio part number is the one your BMW dealership indicated (65129162994), number for number. Funny, the correct part seems to elude the BMW parts people too. You will also need a Sirius Retrofit Kit 65-11-0-432-318 for proper installation.
I was thinking about going the ebay/internet route, but considering the parts & labor it takes, I just decided to have BMW do it, and taking the guess work out of it.