A 1942 Johnson book states that the same tank fits models K-80, KA-37, KA-38, KA-39, KA-10, KS-15, KD-15. They may or may not be identical (needs comparing) but they will fit and function. Many Of these model motors are around so a tank should be most easily available. Doing it yourself can be an interesting learning experience applicable to other tanks which are not common. I did a K-65 tank once which came out very nice, good enough to polish. I cut out a section on the inside face behind the flywheel big enough to access the dents and TIG welded it back together. It takes lots of time and care though.
A KA-39 tank may be a painted tank, which would be easier since bondo and sanding can be used.
