I am not sure I understand what you are asking for. In NWN, a katana has 1d10 damage and 19-20/x2 criticals, just like a bastard sword. Module authors are free to change that, like in the Aielund Saga, in which a katana has 1d8 damage and 18-20/x2 criticals.
EDIT: I didn't see your other identically-named thread until just now. This must have been an accidental double-post.
