I have the same grips and have to glue the left grip. If I don't it slowly slips off and I have to keep sliding it back into position. I'm afraid one day it will actually come off the bar while I'm riding if I don't glue it.
If the inside of the grip is rubber, just spray some hairspray inside it and slide it on. In the morning it'll be on there good and if you ever decide to take it off just blow some compressed air under it.
Glued mine even though the switch housing clamps around it. I don't hold on very tight, so I want what I'm holding on to solid. Would be scared the damn thing would come off, anyway.
In the past I've used hair spray and it's always worked, but for some reason it doesn't work on the ISO grips. Must be something to do with the material inside the grip. So I've used glue this time.