Mark,
I had a look at a M or S 125 the other month. It was in South Western Sydney and was for sale at a reasonable price. Had a later model motor in it so I went with a RM125A instead.
Give me a call on 0407 915 014 and I'll dig up the number for this bloke. Had a perfect original tank, down pipe, usable forks and a couple of other bits. I can help with RM 125 rebuild info to as we have 2 so far and both worked out great
Pete
Wollongong