.5mm Piston wanted

[wes]

Further to stripping my engine after it throwing a rod, as suspected the bore and piston are rather knackered, but the head looks fine with only the smallest mark on the piston where it touched a valve...but will replace the valves anyway.
The engine is running .5mm pistons, and my remaining 3 look in really good shape with a honed bores by the look of it.

Does anyone have a used .5mm piston in good nick?
I am guessing this is a big ask, so if not, does anyone know the details of the .5mm pistons that had been made?

Cheers,
Wes