If you want constant battery power, run the power wire over to the driver side A-pillar. Pop the side panel off the driver side of the dash, and there is an in-line connector there with a red wire to tap. That battery power wire is on a 10 amp fuse, and is only used when the tailgate release button is pressed in the overhead console, if equipped. Otherwise, that wire is not used.
If you want ignition power, and you have at least an auto dim rear view mirror, tap the pink/yellow wire of the connector that is plugged into the mirror. That circuit is on a 10 amp fuse, and the mirror only draws less than an amp. If you have a base mirror, and that connector is not there (the one that would plug into a premium rear view mirror), run your power wire over to the passenger side A-pillar. Pop the side panel off the passenger side of the dash, and tap the pink/yellow wire at that in-line connector. This is the same circuit as mentioned for the mirror, but isn’t used for anything if you have a base mirror.