This won't help much but I will post anyway:Motorola Alternator for Mercedes Benz
http://www.peachparts.com/shopforum/showthread.php?t=245005&highlight=Motorola
Where I have seen Motorola Alternators is on industrial Vehicles like Fork Lifts and Loaders. The last place I worked as a Mechanic was a place that serviced Carrier Refrigeration stuff; including the Diesel Gensets that powered the Refers Units on Trucks or Containers.
The 3 Cylinder Air Cooled ones had Motorola Alternators but they had the ones with the External Regulators.
When we needed a new Regulator we most often bought them from NAPA.