Hello Des,
I hope you are doing well and that the morale holding good.
There was a project in Switzerland to crate a replica of a Dufaux 4N aircraft (if I'm right). The goal was to repeat the flight of Dufaux over the Lake Léman.
The team have a website
http://www.hepta.aero/faux/fr/index.htmlIf you tell me what you are looking for (drop me a PM), I will be glad to contact them (I live not far from Lausanne) to see if they are "open" to share some documentation and information.
Moreover this you can go to this website
http://ba.e-pics.ethz.ch/ and put Dufaux in the "search" window there are some nice pictures that could maybe help you.
"Official Museum" are for the most in the German speaking part of Switzerland, and it could be, unfortunately, very difficult to obtain something if you don't speak german.
Cheers
Dric