Plan B.
Your photos do not show if you have much room above the tire or not, like a handlebar bag. Note the front light I have on my road bike, below. If you have much room above the tire, you could put your light above the wheel.
I used this light mount, it is an off-the-shelf B&M light bracket:
https://www.bikeinn.com/bike/busch-m...nt/137506734/p
If you had the tools to bend some stiff metal like that bracket, perhaps you could make it a bit wider, and cut a 3/4 or 1 inch long piece of round wood dowel or broomstick handle to mount inside that bracket?
When I ordered that B&M light mount, I had no idea if it would work with my sidepull brakes, but it works without any problem, the light does not impair brake operation at all. I can't say that would be true with your brake too or not, but the bracket is a low cost so it is not a expensive risk to try it. I think Peter White sells that bracket, but I bought mine from Europe.