I got some inexpensive under grip warmers with a hi/lo switch and a pair of Tusk covers. About a $40 investment. I taped under the warmers on the left side to insulate from the aluminum bar. Then taped the wiring down good to keep it from being damaged. On high they can get a little to warm, but other wise work pretty good. The only downside is that I cover my levers all the time so my fingers don't get much benefit.
After I put on these covers I realized they were just to tight and made the switch gear hard to get to, so I used a razor to cut thru the stitching holding the two halves together(On the left side in the picture), It was a separate box stitch and the rest of the stitching is fine. There are some thin metal bands in the opening, so they keep their shape. This bike also has hand guards that keep the covers in place.