12111-37401 PISTON (STD)
12140-37430 RING SET, PISTON (STD)
From the agents, both standard piston and standard bore rings are still available. same as circlips & gudgeon pins.
1st oversize only pistons no rings, 2nd oversize neither pistons nor rings.
Now please don't tell me the agents take too long because they don't have 30 year old piston rings on the shelf and have to order from the factory in Japan or they are too expensive.