How about swapping to a different fork? That would be a logical option to me- - - -they're not particularly scarce, and if the ball is worn, wouldn't it be a good assumption to believe the mating part also might have some wear? It would also be a possibility to build up the ball with hard facing welding rod and recontour it with a tool post grinder on a lathe. How about motor mounts? I've solved some pretty terrible clutch shudder problems with new motor mounts. Flathead Fords in the 1940s and 50s had such chronic problems with clutch shudder that there was an aftermarket kit sold to preload the mounts toward the rear of the car. It was most noticeable on the ones with a torque tube rear end- - - -1948 and earlier.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!