Cite International des Arts, where my husband had a residency.
I became a bit obsessed with buying the ubiquitous Mona Lisa cards, especially since I found them at a great price at the book store: Monalisait.
I have 30 of the cards in my possession. I may have sent off one or more, but I can't remember. I do remember that I had a fun time coming up with different ways to alter Mona.
The location that I would buy them at has been closed, I just learned, but there are others. If you are in Paris, check them out.