The aux power socket normally fits onto the front 'beak' panel & the power for it is taken from the OE power socket under the left side of the seat.
It utilises a 'piggy-back' type connector onto the back of the OE socket and is switched via the ignition.
However, there is a dedicated GPS power connection under the front of the tank which uses a connector which matches the plug on the end of BMW's NavII power cable.
Cheers
Dutch