I'm not in your part of the world, but if no-one closer can help you just give me a shout.
What thread does the new nut need to be threaded? I have the standard metric course taps up to M12, and I can single point internal threads ( as long as they are metric, I havent got an imperial leadscrew yet ) but would need a section of the leadscrew to be able to match it to.
Tim