It just have to protect if the chain brakes and gets loose, it doesn't even have to cover the chain.
So after talking with the tech inspector my choice fell on just a sturdy pin.
A really sturdy and rigid pin that breaks the chains path if broken is enough.
"It's up to you if you like to be dirty" was the tech inspector's verdict.
So I took a 10mm steel pin drilled a hole in the fenderstrut and welded in the pin, and suddenly I had a chain guard.
The hole and the pin
The two joined with some welding.
I might cut it off just a tiny bit, time will tell.