3/4" aluminum box extrusion and 3/4"x1/8" aluminum bar. Two bars to the license-plate mount, and two to a pair of holes conveniently located behind the grill, just above the bumper-beam. Not the most solid, but solid enough.
If I wanted to get fancy I guess I could get a fog-light switch from the dealer. This works.
Here Moosey-moosey-moose...