Nah sorry, no bits for the little fellas.
It looked to me like the muffler on the twin is alloy. Is the muffler on the little ones alloy too??? Im sure it wouldnt be too hard to make up a steel copy of an original muffler.
If you keep your eyes peeled im sure you will turn up an O/S piston and rings set for it. All it realy needs is enough compression to fire up. Its not like you will use it as a hard working mower.