Hi
I thought you might want to have a look at what is available on the main gun auction site in France.
Many gunshops seem to be using this as a route to sell their new guns as well individuals wanting to trade their own guns.

Copy and paste the link below into your web browser.

http://www.naturabuy.fr/Express-cat-131.html

If that doesn't work just type - Naturabuy - into Google and it should take you there.

Key words to help with your searches
Fusil de chasse = shotgun
Express = double rifle
Combinaison = combination
Juxtapose = side by side
Superpose = over-under
Platines = sidelock
Ejecteurs = ejectors
Extracteurs = extractors
Mono-detente = single trigger

If you have any problems with translations let me know