They are not an uncommon motor but there is a strong demand.
Cub and Mate parts don’t often come up for sale.
Most people, like you, that have an incomplete
motor would rather hang on to it hoping to get
the parts they are needing. When parts or a parts
motor comes up for sale they go quickly so you
need to be pretty dedicated in your search. It not
imposable to find what you need it time. It can
take years to find stuff for these early outboards
but when you do find what your looking for its like
finding buried treasure.The searching is part of
the enjoyment of the hobby.
A "Boat House Repair" is one that done without having tools or the skills to do it properly.