My hands used to numb after a time on a motorcycle, probably due to buzz in the handle bars (1 cyl., 3 cyl., 4 cyl., made no difference). I bought a pair of
Qui gloves which I'd say have been 90% effective). Of course my hands would numb some due to cold. Heated grips usually take care of this for me.
Regarding throttle locks...I've never used one but would not be afraid to try one. Like John said, most do not lock completely. The right size O-ring might just get the job done and maybe confirm the effectiveness of that type of device on your problem.