BMW sells a navigator mount for the 660 and Navi IV (which is a 660 of a different color)
Here is the 660 installed:
Rode with the 660 for about two weeks but hated using the touchscreen with gloves (too much attention away from the road), so I exchanged it for the Navi IV, whose mount has large, haptic buttons on the left. And they're backlit.
See more GPS photos in the link under my sig.