Good morning, Agswitzer.
In the general case, such items are cheaper and still readily available from sources other than the manufacturer, in this case Yanmar
. Yanmar did not design the rings. They used appropriate ones off the shelf. They will charge more for having to stock them for a small market, while the same rings fit other engines as well, and an engine parts
house, with a wider market, will not only have them but at a good price
. In this case, simply Googling "Yanmar 2gm piston rings" revealed them at "Parts4engines".