I don't know about engine sprockets, but in years ago we used to make gearbox sprockets from
industrial ones and they last long enough. Maybe you can take a file with you and test
the hardness. We simply cut the center off in lathe and weld it to the new sprocket.
Ariel VH 1954, IZH 350 1962, H-D Sportster Hugger 1992, AOMCC Member 133