KB
Herve Bruchet has a workshop now, I do not know how far he is from Paris. He might be worth a look, both because he knows Darnes and because he speaks English and knows gun terminology.
If you can go beyond Darnes, and are not bound to a name, you might find some interesting doubles unknown outside France. Even some cheapos like the Tarzan (the name says a lot lol) can give you superb balance in a rugged double for a very small outlay.
Here is Darne's site
http://www.fusildarne.com/gun-sporting-gun-darne