I beleive (dont trust me 100%) that you want a 19x20 master cylinder for the NSR250. You can pick up a brembo or an OEM from other bikes that use the same size master cylinder.

As for the body work, if you go with aftermarket, make sure it ABS and not PVC material (early Chinese stuff was PVC and crap, most new stuff is ABS). or go with FRP/Fiberglass body work (Tyga for example).