I've had a look about and the sleeve seems easy to get hold of.
This one here
The piston seems a bit harder, I can't find anyone who does a piston that big for a DT or WR200. I have found some big pistons for Yamaha Blaster quads which I believe is the same engine as a DT/WR but with an aircooled top end.
Not sure is these will work 72.5mm and 72mm Not sure on the pin size though?
Any tips?