ah, ok thanks. Where would I get one of those and are they a standard fitment?

If you want one that gives you a lighter action see Nelly/JHP.

you could opt for a 19x20 which if you have a std slave cyl wil give you a lighter clutch

ok, that might be the way then coz the italian geezer sells em at the same price

You've got it reversed: the smaller the clutch master cylinder diameter -the lighter the pull; the larger the slave cylinder diameter - the lighter the pull. So, the (early) 13mm stock master has a lighter pull than the 16mm Brembo radial which has a lighter pull than the 19mm diameter of the 19x20.