Busch & Muller have 2 nylon ,( no vibration induced metal fatigue, then) headlight mounts
1 to fit in spacer stack on thread-less headsets,
and another to fit like a washer between the adjustable race and locknut. on threaded fork headsets..
The design of B&M dynamo powered headlights these brackets mount, is such as to have the shaped light beam cut off to
not dazzle drivers eyes, by not having the reflector around a centered LED as if a flashlight..
there are several pieces made by a number of companies , to place a handle bar battery mounted light on a second tube beneath the handlebar.. a second threadless stem beneath the other, with a section of straight tubing on place of the handlebar can do that as well..
https://www.bumm.de/en/products/mehr...0brackets.html
https://www.bumm.de/en/products/mehr...t/471b-1.html?
...