So buy a 10 gal and only fill it half way or 3/4 of the way as needed.
if ya bound and determined to sue a 7 then any good welder or black smith can easily make a 10 gal stove fit.
A way I have seen this done is to simply tack a few chocks(shims?) to the inner ring where the pot sits. My rule is use a bigger pot than needed so ya have plenty stirring room. It's tough when the pot is full to the rim.
