A fork crown usually has a hole,
Seen: there is a low cost battery 5 LED light, that screws to it,
via a bolt thru the hole.

You have a hole there? usually handy for mudguards too...

its like a regular headlight, mounts like one..
I saw it in one of the catalogs at the LBS
I'm sure they could order and re ship it..
there is a red one too..
I can look it up, during my next visit.

I have my dynamo powered head light mounted lower,
so I don't drape my cycle rain cape over it.