As Koyote advised, you could try Sanford/Waterman in your country, but I doubt they will still have parts for that pen left.
Waterman concentrated repairs some years ago to the plant in France, and this now is moved to (or will move soon?) to Poland.
Even nibswaps on new pens had to go through France, although sometimes the local branch would just swap a unit with a new pen they had in stock (as has happened to me..)
There are companies that still have stocks on nibunits on past models, so you could try to google the internet.
Sometimes shops like Nibs.com carry them. (just checked, not at this moment)
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