in the town where my GF lives there's a guy doing gears for vintage rally cars.
showed him a pair i needed for my supermono, he could replicate them no problem, but setting up the machine for just 1 set puts you in the hundreds of $/£/Euro range per unit.
if you can pool some people into doing a small run gets way cheaper... but cant think that many guys racing kawasaki 2 stroke off-road singles!