I adapted the door-key pictured below, to help one of my consumers with severe neuropathy in his hands, insert and turn it in his door lock.   I used an epoxy putty (available at most hardware stores).  The stuff comes in the consistency of molding clay.  I have seen different types, but the one I chose has a portion of the putty that is white, and a portion of the putty that is black.  By thoroughly kneading together, two same size chunks -- one white and one black -- you come up with one gray chunk.  You can then mold this chunk around the grip.  I used a nail to make a hole through the key-ring hole.