Perforated galvanized plumbers strapping. While most of my equipment is wall mountable, I used exactly this sort of thing for all the power supplies.
Likely similar to whatever you're planning to use with the plastic strap, but more metal is more betterer
I believe the term you're looking for is skookum
Yeah the plastic version of that, easier to work with and I want to give the lutrons rf as much help as it can get.
Coat hangars or aluminum wire. Loop for a screw, bend to the shape you want, loop for another screw. Or eye screws and zip ties.
If you have a well equipped shop, I assume you have old wood laying around. In that case, whatever you end up doing, i'd suggest mounting it to a thin piece of plywood first, and then mounting the plywood to the inside of your closet. You could use a French cleat if you want to be fancy, or just use some pan head screws at the top (and bottom if you're paranoid) and then take them out and drill out the holes in your plywood to just barely more than the size of your screw head. Put the screws back in the wall and use it like a keyhole. Now you don't have to screw around inside your closet when you need to rearrange again. Just pull out the whole panel.