If you looked at the link I just posted, you would find:

- the bracket is $65. The part # is included and you can order that online or at the dealer's parts department.
- the bracket fits and Garmin GPS. Yes, even the cheap $200 Garmins at the store.

You can do this setup very cheap...

GPS Install Kit, part #: 65900445996







According, to this article, the unit is just a Garmin 760.
Garmin Decks Out BMW, nuvi Style - U.S. News Rankings and Reviews


Which is $235 on Amazon.
Amazon.com: Garmin nüvi 760 4.3-Inch Widescreen Bluetooth Portable GPS Automobile Navigator: Electronics


You can retrofit this yourself for $310. If you already own a Garmin, you can do it even cheaper. My old nuvi 670 and 200w fit just fine...