-
You would use one of these...
https://www.rockandrollbikes.com/weinmann-front-brake-curved-washers.html
-
@AlexD this was what I was going to suggest and file one side of it to sit flush on the front of the fork.
I think I’d drill it in the material just below the unicrown, but stick a wheel in and measure where the caliper drop ends up first (in case it puts the caliper in the wrong place). If you have a few calipers knocking around on other bikes it might be worth eyeballing them in case one of them will work better. I happened to have a mega low drop Campag caliper that fitted my fork a lot better than my intended single pivot Shimano 105 was going to.
They reckoned £45, which I think is their minimum charge (I seem to remember drilling a fork being listed as about £25 on their price list).
@Rodolfo was your fork exactly the same? The thing I’m struggling to visualise is how the nut (? Where it goes in to the calliper) of the brake bolt would have space to sit flush against the fork.