Otto Gas Engine Works. http://WWW.Ringspacers.com is the web site home. Specializes in piston rings and piston ring service.
Two page flyer returned with ordered piston ring indicates that this firm makes piston rings. Ring bore diameters from 1" to 84". Lists rings, head gasket material and some parts for antique Briggs, Fairbanks Morse, IH and Maytag engines - hit and miss.
The reason I am endorsing this firm is the service. Outstanding.
Two weeks ago I emailed several piston ring manufacturer asking about the needed piston ring. About an hour after posting the above message praising Otto Gas Engine Works for their service, I received a response from one manufacturer offering to sell me the piston ring.
The ring has been received and the piston installed in the engine block.