After looking at all the usual ways of getting shore power into the van I decided to go with the idea of having a separate box under the rear bumper. This is not new, or as imaginative as putting the receptacle in the bumper or in place of the reflector but does have a few advantages. At this point I do not have the electrical loads to justify installing a larger capacity plug although everything is open to change down the road. I used a piece of the same channel as the roof rack towers are made from and cut it to mount to one of the trailer hitch bolts that still had enough unused thread available. The bracket was drilled out to give clearance for the waterproof gland coming out the back of the box, then all seams and water entry points were sealed with silicone. Might spray it black later if paint will stick.
I may end up moving this to the other side if I install a swing out tire rack on that side.