With arthritis and possibly a bit of carpal tunnel syndrome, it is the vibration that is really aggravating those conditions. So a softer, larger grip may help dampen some of the "buzz" in the bars. But it may not be enough. I agree with the comment above about trying to release the "death" grip you may have on the grips too.
But another possible solution might be trying a bar snake. These change the vibration harmony of the bars and tend to neutralize the vibration. See here:
Harley Davidson Community
TQ