Hello, I'm also looking for parts for a B & K, I found this reference online store that works with pieces of this brand. I do not know if they have all the parts advertised do not know if they serve to advertise you (do not know anything about boats) but try to find the parts you are looking for while I look for parts for my engine.
Try to see this site "Ellwood Hobby" (if you have not seen).
Ellwood Hobby
http://www.angelfire.com/pa4/ellwoodhobby/
and also the specific listings of parts for K & B 7.5CC
http://www.angelfire.com/pa4/ellwoodhobby/7.5cc.html
Hope that helps in something, but know if you still looking for things always look on ebay and if you step to find something.
Hugs
Jorge