A nice simple mod this and I make no claim of originality of thought. An easy project for a lathe rookie like myself: particularly useful on an occasional recalcitrant starter like a Velo where every so often you might engage in several energetic lunges at the kick start and then, just at that point where it seems like your luck is at it's very bottom and you are exhausted, the kick start rubber falls off as if to mock you.
The job took even a very amateur lathe-ist such as I less than an hour to do. First step is to take off the folding part of the kickstart off sans rubber, put it in the lathe and face the end off flat. Source a suitable countersunk machine screw and then drill the appropriate sized hole in to the newly faced kick start lever. Tap the hole for the machine screw and the job is half done. Next step find a suitable piece of scrap alloy and drill and countersink it to suit the screw, turn down to size, shape with a file and cut to length. All that remains is to cut a hole in to the closed end of the rubber, assemble the lot and presto - detaching kick start rubber woes gone.