I had a simular problem with one of my competition grips and I was able to solve the problem by using Dow Corning Clear Silicone Adhesive, I placed a uniform thickness layer of Silicone on the inside of the grip and riser and then slid the grip onto the riser and then either tape or tie the grip in place, remove excess silicone that oozes out around the grip and let set up for 24 hours.
Hope this helps ya
I would avoid the crazy or super glues, they can damage the finish on your riser , and if you decidde you would like to try a different grip in the future you may have a hard time removing the super glued grip.