Motor mount yoke is different on A & B-engine - where to source a B one?

[nuwala]

Today I managed installing a restored B-engine in my Model A. Everything matched well, except the front motor mount yoke. The motor mount yoke is to wide for the timing wheel cover.
I checked the larger known web shops for a B motor mount yoke, but could not find one.

Where could I buy a B motor mount yoke?
Where could I find a drawing to build it myself?
Is there some kind of adapter - A to B - in the market?
e