I have manuals for the 1C, not the Valoy. And it is the first time I hear about this "shim". Anyone who has such a manual and could scan the page?
Anyway, I also think you are right that it won't be difficult to fabricate . . .
I also have the Valoy II with the AN condensor, this works fine. However, I like to have the use of both systems.
Beautiful enlarger btw !!