the front master cylinder rebuild kit is factory part # N0220.F with suffix L19C
any H-D/former buell dealer should have them in stock. very common kit for many applications.
if no luck there go to either new castle H-D or St. Paul H-D website, enter that part # and order up.
NOTE: you'll have to lightly hone the bore of the m/cyl properly to assure smoothness and no nicks or corrosion or all the new kits in the world won't work correctly.