BTW: Post this in the French section, even with google.translate you'll get great results!
When I lived in Paris, I have used 3 areas:
- the steets around "La Bourse" (the old sock exchange has/had a dozen of shops specializing in coins (just behind Les Halles).
- there were about 3 shops, concentrated on Montparnasse, next to each other, close to Tour Montparnasse.
- for cheaper finds go to the flea market at Clignancourt;
- But if you look for mint issues, just go to the mint:
http://www.monnaiedeparis.fr/ 7 minutes walk from the Notre Dame. They have everything they have minted recently; although the staff is very arrogant.
Good luck!