I had the same problem, the clutch side grip wouldn't stick the heavy knurling on the bar. Grip glue solved it. The local shop had a small tube for something like $2. I'd think most any general epoxy rated for steel and rubber would work. Else there's always safety wire.
This shall pass, be still and know.
2006 XT225, UNI filter, ProTaper bars, MSR handguards, SS front brake line, Shinko 241's.