Jonathan Takagi sent this information, which might be useful also for people outside Paris and France.
If you're interested in Godard posters, check out "Les films du temps" on Rue St-Martin (right around the corner from Hôtel de Ville) in Paris.
They have posters from most Godard films and are extremely accomodating to requests, special orders and mail orders.
Here's the info:
AUX FILMS DU TEMPS
8, Rue Saint-Martin
Monday: 14h- 19h30
Tuesday-Saturday: 11h30- 19h30
Métro: Hôtel de Ville or Châtelet