Mine recently came off 1200 miles away from home on a Sunday, I tried hair spray but it didn't work, i'm thinking that they don't make it the same as before. Ended up using good o'l krazy glue, i did not want something that permanent but i didn't have much choices that day. If you go with Gorilla glue be careful according to the instructions it expands about four times it original size. If you can i would recommend something less permanent.
+5 on the electrical tape. I have used that on all my bikes and never had a problem. Wrap it then twist the grip on in the direction of the wrap. Then when you need to take the grip off a little force and it comes off.