Rings, Piston Part # 39-21665 may still be found. Try Ferguson Poole,
East Coast Marine and other online sources. These rings were used on
the 3 ring pistons of 5.5 cu in singles and 11 cu in twins made by Kiekhaefer up thru KE4/Mark7 and Wizards WG4. So the OEM rings
should not be all that hard to find even today. Otto Gas Engine is a specialist source of rings either from stock or custom made. You have to be
able to say what size you need.
Louis