No.401 is also found to be for sale. The seller is located in Chagny, France. It is advertised here:
https://pro.annonces-automobile.com/rare-et-dorigine-acl/citroen-m35-4775885
Thanks to Chris Kok for spotting this car and also discovering number 438
The text of the ad (in French):
Très rare Citroën M35
1970
Moteur a piston rotatif Wankel
Seulement 267 exemplaires vendues par Citroën entre 1969 et 1971
Voiture en état, roulante.
Intérieur en très bon état.
CG collection.
And the ads maybe gone soon, so here are some more pictures:



