Hello, I live in Belgium and so understand your cravings. We are lucky as just outside Brussels there is a fantastic english supermarket, which we go to when we are desperate.

However we always ask guests when they come over to bring sugar free squash and tea bags as these are things that we use loads. Dependent on where you are in France perhaps a trip to Belgium is not out of the question so you can visit Stonemanor (check it out on the web).
BTW does anyone else find it difficult here in mainland europe without the help of sugar free items ?? Squash being one of the biggest needs, also for the kids as sugar sirop is the norm and seems crazy!!