Oh that’s a shock.
Friends of ours lost their rudder mud Atlantic (hit container?) but got to Carribbean. Not a Dufour. They found it easiest to get a new rudder from their boat manufacturer even though that model was no longer made. They have the specs etc. so going via a Dufour agent and direct would be my suggestion. Don’t forget to do what your insurer says too.
The membership association for owners of Dufour Yachts