Bill, I think I have one older MAX .19 and will check the drive washer. That vintage of engine had the drive washers with the D shaped hole. You may get lucky and one from something lese may fit, like even one from a LA.25. It's over 100 degree heat index still here at 10PM but a cold front is supposed to be going through tonight. When it cools off up in the attic tomorrow I'll check it out. They made a .19, .20 an .25 back then that may be candidates.
Type at you later,
Dan McEntee