Old off road tricks -
Hair spray - back when most were some sort of laquer type, don't know how the new stuff works
Spray paint - most garages have a can of something sitting around.
I just did spray paint on the grips for the Zephyr - Rustoleum semi-gloss black for those who might wonder.
Sprayed it on some cardboard, wiped a paper towel in it and smeared it on the bar/throttle tube. Then I used an air gun to blow the grips on, having blown off the old junk ones. The paint sticks them to the bar/throttle tube.
KLX650C, Zephyr 550
SR500, Bultaco Sherpa T