It's been a while since I've been in Paris, but I always shopped at Prophot for film whenever I was in the city. Be warned though -- film in France is expensive, so it's better if you can bring your own. In French "argentique" refers to film (silver-based) photography, both colour and black and white, where as "numerique" is digital (not sure what your French skills are like, just thought I'd mention it).