All I can add is that if you remove one (or more) of your silver roof bars/handles (six 30T torx bolts) the plastic dish behind the bars comes out and there is a hole in the roof leading to the interior of the vehicle. You would have to drill a hole in the plastic dish to feed wire. Shouldn't be too hard to use the 10 amp in the footwell, (Int 1 or 2), to feed a relay and take your power from the battery under the seat.
Of course it is all easier said than done. I'm in the same boat as you. I got the locking diff but my off the lot vehicle didn't have the aux power... I should have shopped longer and found one.