Ted, Sorry to take so long...
Try:-
http://coxengines.ca/This is an outfit in Canada which has a lot of Cox goodies. Among them are - usually - the owners' manuals for most Cox engines ever produced. They also sell the prop sizes you need, which are almost impossible to find stocked in the USA where the emphasis is on larger RC products.
Prices are, well, not what we recall from days gone by, but - today - are reasonable. Service is quick and satisfactory in all ways, in my experience.
Luck and good flying!