The fork crown has a hole for a brake bolt. This is a useful location for a
lamp mount and a standard location for dynamo lamps.
I've tried a number of different mounts, some interfere with the headset race. Plastic ones are not usually strong enough. Old, steel reflector mounts are good. I made one out of scrapped aluminium cranks and some sections of old chainring.
The Busch and Muller style thick steel wire loop is very strong and reliable.