I took off the multifunction switch housing from the handlebar and the simplest solution would be to wrap a piece of tape over the hole. When the housing is put back on the handlebar the registration pin would push into the tape thus still doing its job of stopping the housing from spinning on the handlebar and hopefully stopping any BB's from getting through the hole. I have not checked the throttle side housing just yet.
My only fear with this solution would be that over time the tape might wear and eventually allow the BB's into the switch housing again.
My only fear with this solution would be that over time the tape might wear and eventually allow the BB's into the switch housing again.