Ignition Rotor Adapter

[Dave Rutkowski]

I have an '81 635 that uses the ignition rotor that presses on to the front of the camshaft (p/n 12 11 1 286 072). Last week mine sheared off its indexing key (while on the track...that was exciting), backfired pretty explosively for a bit, and then the motor quit. Put the old rotor that I had saved back on, and everything is back to normal but I'd like to prevent this from happening again.

I understand that BMW made an adapter that allows the later bolt-on rotor style (p/n 12 11 1 734 110) with corresponding later distributor cap to be used instead of the push-on type. Had a BMW p/n and everything, but apparently is now NLA. Is anybody familiar with what this p/n is, and where I might source one?