I recall seeing some form of knob that could be attached to a fork blade with a zip tie, but do not recall where I saw it. Did a google search and saw this graphic:

Graphic from: https://www.peterwhitecycles.com/dualsetupfork.htm


Or, I think you have a hole through your fork crown, as it looks like you have a fender mount bolt there. There are lots of light brackets for a fork crown. I could not find a long enough bolt for my light bracket on my fork crown and fender setup, so I bought a piece of 5mm threaded rod at the hardware store, or maybe I used 6mm, I do not recall which. Cut that with a hacksaw.



But I can't tell from your photo if there is enough room under your handlebar bag, you can see in my photo above that I had enough room for it.


Or, you can buy a knob that you can thread onto a quick release skewer and put the light on that knob. Looks like you have through axle, not quick release. But since you have a fork mount for your fender bracket down there, you could thread a knob onto that. This one is a bit pricy, I seen things like this cheaper elsewhere. But mounting a light this low is not ideal, you get large shadows behind things like leaves, etc., and it is harder to see how big bumps are when there are really big shadows behind the bumps.
https://www.campfirecycling.com/prod...nt-p-2576.html


You have to think outside the box for this kind of problem.