For years I've been wrapping my foam handles with equine tape (from TSC), but decided to just replace them with rubber grips. It's simply a matter of removing the arm-cuff and adding a small amount of dish soapy water to slide the grip into position (after carefully cutting the foam grip off with a razor blade).
I also did my Compadre (not pictured).
The challenge was the DeLeon, since the battery box hangs under the arm-cuff (meaning there's wiring involved), so I un-soldered the battery connections, removed the cuff/battery box, added the grip, and soldered the connections back into place. I did remove the control box, just to protect it while working on the rest of it. The power wiring unplugs inside the box, and one screw under the box has it off, out of the way, and safe in a couple minutes.
Besides the fact I can now wipe these clean with a damp cloth, these grips are larger, and feel much better in my (larger) hand.