GPS installed, but need good power source

My buddy at work bought new Garmin GPS for his BMW 525 and installed it in the top corner of the dr. side A pilar, but there is no easy way to get power to it. Any suggestions?
I will post in the BMW forum too, just in case.
Thanks!

run the power wire down where the a-pillar meets the dash and route it under the dash to a fuse box