There used to be a 'guide' but recently a lot of municipal sites are being 'sold off' by the local councils - and so I think the guide quickly went out of date.
You could try the French tourist office, but it's probably better to have a look at campingfrance.com (which contains details of all 11,000 sites in France) - and look at the areas of France you want to visit, then the facilities you need on site, and select with the search facility. The Caravan Club, Europe 1, also includes municipal sites, but not as a separate category. There are some equally good value privately run sites - particularly 'Camping a la Ferme' where you can be the only visitor, in an idyllic orchard somewhere - and farm produce to buy on your doorstep or a lovely meal with the farmer and his wife!
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