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You might have to find a friendly Vintner who will be willing to do this for you. No retail outlet that I am familiar with would do this.

I was told locals know the places. Vrac en vin ? Cooperatives and caves.

Depends upon where you are. In Paris (and likely other larger cities) there are places that have wine in large barrels and can either fill your container or sell you one.  Le Baron Rouge is one such.

In Italy I’ve seen coops where you could fill from what looked like a gas pump built into the wall.

In Austria you can go to any Wine tavern and ask them to fill up your bottles. I can't see an issue in France, you will just need to ask. I have 7 wineries in my town here in Austria and quite happy to fill my containers.

@SGfrance

You speak French. It would be a dealer in a village or at the village market.  Since my father-in-law died, I have not had a connection. The seller at the weekly market may or may not pay tax. I do not ask. 

@SGfrance

Some cave cooperatives have large tanks of wine. They will fill your tank or thermos or whatever you have and charge by the liter. I also recently went to the best wine shop in the south of France (). They have the biggest tank of wine I have ever seen!

Wine is food; it can be found anywhere in the southern EU. You keep your eyes and ears open and ask if you can. A bar is a good place to ask after you have been there for a while. Being a customer always helps.