The actual drive is probably not around (if even made for these engines) but not difficult in an engineering sense. Under $100 will buy all the parts, the method of attaching the drive to the crank and blower rotor are the puzzle.
2 roller chain sprockets, I suggest #50 (a.k.a.530 single row), tooth count 17 minimum, 60 maximum but obviously limited to what will interfere with something.
1 length of quality #50-2 (double row) chain = to the circumference of
one sprocket.
1 sprocket is attached directly to the crankshaft nose (like any blower drive, keyed, tapered, whatever).
The other sprocket is attached to the drive end of 1 rotor.
The chain has one row of rollers on each sprocket, face to face.
This is 100.000% accurate, only needs to be greased, very durable (nervous? Use #60 chain), weighs almost nothing, and yet allows for very small vibration, misalignment etc. that would break a "greek" (male-female) coupler.
