I have numerous bike lights I use for both road and mountain biking at night. I'm well aware of how they work and what the beam patterns are like. Whether mounted horizontal or sideways...You are splitting hairs.

[MENTION=413198]prj71[/MENTION], thank you.

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.

https://cimg5.ibsrv.net/gimg/bikefor...9ae6145238.jpg

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.

So what kind of contraptions are occupying the handlebar that mounting a light is out of the question?

FWIW, here's something I did about 13 years ago, when I needed to mount a light to the fork blade of a recumbent.
It's pretty basic... just a "T" shaped bit of steel and two hose clamps. These were standard stock items at the local Ace hardware store.
Well, I did put a layer of old inner tube around the fork blade before clamping the T-shaped bracket with the hose clamps, but that's about as complicated as it gets.
Not the prettiest thing around, but functional.

https://live.staticflickr.com/4083/5...ac09c3_c_d.jpg

Steve in Peoria