In my experience, it is the cheapest item in a company's inventory which is most likely to result in a poor customer experience. It doesn't matter how good your *important* products are, if you don't take care of the incidental parts everything can go wrong.
Take the B&M light holder; designed to work with Cantilever brakes, the fitting bolts to the fork crown then the shaped metal drops underneath the cables and comes up again to be in the perfect place for the light.
It looks to me like this is an outsourced part because the Spa Cycles website has a similar looking piece labelled Schmidt Cantilever Brake Bracket.
Everyone is at it, here is the AXA bracket:
Looking at the SJS website, there is an expensive CNC machined part, Thorn Alloy Dynamo Headlamp Bracket; which is claimed to work with Cantilever Brakes; this is clearly a different design altogether, but from the photo and the website I cannot tell whether this would fit. How long would the bolt have to be, and how strong, to run through the fork crown and then through the spacer?
Another alternative is to mount the dynamo light higher, on the handlebars instead of the fork crown, but this may interfere if I choose to fit a handlebar bag for touring.
Lots of thinking and research to do, and clearly I have no intention of replacing like with like. Any variation on the B&M cantilever bracket is just going to be another waste of money.