Make 'em!
Old school stuff needs old school approach.
I made mine out of wood but you can use aluminium, polycarbonate, or even Tufnol for a real OS solution.
Just work out the PCD (Pitch circle diameter) of the teeth (10), drill with a 8mm.
Drill centre hole and bush with copper tube.
Sandwich between two washers.
Hey Presto!
Job done.
Ask me for a photo.
Nick T