I like the Glove-Box-Light-wire-tap idea, but I take my GPS off the windsheild all the time and put it in the trunk due to theft concerns. (I can see some creep cutting thru the $2200 top to get my $150 GPS.) I like Anthony's idea of the permanent-mounted outlet - as I could use it to charge GoPro batteries and even my phone; my FRS radio and GPS are powered off a two-way adapter via the lighter socket.

Yea, on trips like the Dragon, I have up to four things to power in the car!