Bad luck for sure. Do you still have the small piece that broke off? If you do, you could try a 2-part epoxy to glue it back together. In the U.S. we have a product called J.B. Weld - it's a metalized epoxy that I've used many times to repair broken metal. There may be a similar product in France that you can find.
If that's not an option, that piece can probably be replaced by prying off the old stopper box and crimping a new one on with a pliers.
Best of luck!
Noel