Dennis Trevathan makes mufflers and some other parts for the A Johnsons.
dtrev@comcast.net
Art decalb also makes some parts. He has the air intake tube but it will be
a rough cast aluminum part that will require some finishing.
http://precisionservoutboard.com/
Most parts come from other motors. You can place an want add in the
Free Classifieds section. ( read the rules before posting)
EBay is also a source good for parts.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.