I've been looking and looking and I finally found a nice little art store here in Paris! The name is Loisirs et Création. The one I found is at Centre Commercial (Mall) Passy Plaza. The nearest metros are Line 6: Passy, Line 9: La Muette, and RER C: Boulainvilliers. They are the first place I've found that has Fimo, that means I can now get back into making prototypes for pewter casting! I don't have the equipment to do the pewter casting itself, but I can at least improve my skills by making prototypes. They also have fabric glue at a good price, which means I can attach the backlog of patches I have to my instrument case. There is also a nice variety of brushes, drawing supplies, painting supplies, beading supplies, fabric paints, etc. Admittedly, they aren't the largest of stores, but they have a fair amount of what most people need, especially me :) It's the closest thing to a Michaels that I've found in Paris. They have some other sites at C.C. (Centre Commercial) Crétail Soleil, C.C. Evry II in Evry, and C.C. Les Passages in Boulogne.

Loisirs et Créations
C.C. Passy Plaza
Galerie Commerciale Passy Plaza
53 rue de Passy
75016 Paris 
M 6: Passy
M 9: La Muette
RER C: Boulainvilliers