Not many around--that's the problem with these old Avery's and MM/BFs--hard to find parts and the parts tend to be expensive.
The engine in my MM/BF had zero compression on three cylinders and 25 psi on the fourth. I generally don't buy tractors that aren't running. But I really, really wanted that MM/BF (I collect high crop tractors with bull gear rear axles).
The parts (pistons, rings, valves, etc) to rebuild that 4-cylinder Hercules engine in my MM/BF cost $800 (new old stock (NOS) from Hercano). I spent another $800 in the machine shop getting that engine rebored, block surfaced, head milled, flywheel clutch surface machined flat, reassembled to the short block configuration, etc. These old ladies become money pits in a hurry.
Good luck.