Good luck with these. I had such a rubbish time trying to sort some out for a project, that I gave up and bought a new bike!
EDIT: You can also try on ebay, where they show up occasionally.
Unfortunately, there are differences in thread width, but also in the size of the thread itself – coarse or fine.
Old thread here…
As a result of that thread and my abandoned project, I have two spare sets of canti bosses – 8mm and 10mm that you can have for postage(ish) to try your luck with as they didn't fit my frame.
Gimme a shout if you're interested.
Cheers
Crispy