The two wire regulators are still available new, and there was a technical service bulletin issued in March of 1988 that explains how to to the conversion from 3 wire regulators to 2 wire regulators. It's under repair work order number 72/7. It gives the part numbers for everything you need and how/where to mount the extra parts. The harness for the conversion wasn't ever something that was available because it had to be made up on the spot.
Stanford, if you are talking about the regulator, itself, order a new one from Tom. I think these are cast aluminum but subject to metal fatigue. They bend over time but break when you try to straighten them.