I thought the Widder heated vest thermostat was dumb because it sort dangled around and didn't really feel terribly secure. It was also difficult to adjust.

Heat-troller makes a thermostat that has the potentiometer on the end of a long wire that can be remotely mounted - either surface mounted with velcro or tape, or an integrated version designed to be installed into a housing or fairing. This would also work fine with other heated items like gloves or grips.

I bought one of each style to see if I could fit it into the switch blank on the right throttle grip housing (planning to return whatever one I didn't use). The integrated version seems to fit with a little modification. Although you lose the LED unless you want to drill a hole.

The housing with the switch blank removed.(I saved the blank if I want to reverse it later. You'd need to hack up the insides of the housing a bit more if you want to drill a hole into the blank. You'd also probably have to epoxy or glue the blank into place, since the way it is held into place would probably be hacked up.)
What's inside it
The surface mount and the hardwired heattrollers Just a comparison - the surface mount one is intended to be velcro'd some where. This was plan B.
Needed to trim and modify the circuit board to fit the housing. You lose the strain relief, but the housing pinches the wire pretty well after routing. I used a file and a box knife to score and trim the circuit board.
Another picture of the damage.You can see the board has been filed up to the back of the pot to shorten it, and the LED piece just dangles. I covered it in shrink tubing inside the grip housing.
Test fitting. Just fits in there.
More test fitting. I trimmed the throttle grip housing with a pair of wire snippers and more filing to form around the threaded part of the pot. I'll probably fill the gap with a bit of RTV.
All fitted, still need to run the wiring.
Another final image