Yamaha engine bits
I rebuilt an ME370 a few years ago and sourced the pistons via Kilmarnock Engine services, they reground the crank, cut the valve seats, skimmed the head, etc for me. They got them from A truck part supplier in Germany.
Different engine, but maybe worth a call?
I must go down to the sea again to the lonely sea and the sky
All I ask is a tall ship and a star to steer her by
the wheels kick and the winds song and the white sails shaking
a grey mist on the seas face and grey dawn breaking