If you're building or restoring a police model Moto Guzzi -- either a loop or Tonti frame model -- I may be able to help you with genuine Dietz spotlights and turn signals. Please check out my listing in the classifieds.
Dietz was a manufacturer of a wide range of automotive lighting, beginning in the kerosene lamp days up until the 1970s or 80s. When you see a true police-model Guzzi, it likely has Dietz pursuit lights and turn signals. Harley and Kawasaki police bikes frequently used them too. Dietz has long since gone out of business and genuine Dietz lights are getting harder to find.
I have quite a few of both the pursuit spotlghts and front and rear turn signals in used or New Old Stock (NOS) condition. Price depends on condition, but I should be able to offer you a better package than you'll find on eBay or elsewhere. Lots of pictures available on request.