JB will work, but have you tried tightening down the switch housing (with the nub in the oversized hole) on the handlebar? You may find that the clamping is enough to hold the housing in position. Some people who replace their handlebars with tubular bars have removed the nub, rather than drilling a new hole, and just relied on the clamping force to hold it on. Just a thought.
Gary,
Yes, I have tried that...as I stated in the OP, it still allows 1/4" - 1/2" when the screws are tightened...to a point where I am unwilling to tighten any more! I'm just not OK with the throttle tube moving that much...it's easy enough to let the JB set-up and re-drill...anyway, the forecast shows lots of rain for the next few days...
Thanks, guys, for the votes on JB Weld...it's in process now!