Adding A Cigarette Lighter Receptacle?

[win4wiin]

I want to add a hidden cigarette lighter receptacle either under or inside the dash to power my aftermarket gps nav unit. I planned on using an Add-A-Circuit fuse holder to tap power for the receptacle. Any suggestions on which fuse to tap and the best place to ground the receptacle? If it makes any difference the most likely install for the GPS will be suction to windshield with the wire running under the edge of the headliner and down the A pillar to get under the dash. I am trying to keep the GPS both easily removable and as stock appearing as possible.

 

Thanks.