If you can read French, or would like some practice trying, this book, Paris Bio, is an invaluable resource. It lists and reviews over 150 organic restos, groceries, wine stores, bakeries, beauty, déco, etc. along with contact info and store hours. More often than not, organic establishments have a good vegan selection (except the butchers!)
Carried by most bookstores (and also at fnac.com with free delivery), this fun and handy “Paris est à nous” series of books is easy to find and 100+ pages will only set you back 6 euros. This is a new edition from May 2008 combining organic food and organic beauty. Very current.
(Also on the shelves, you’ll find the slightly outdated Vivre Bio à Paris [September 2004] and Belle et Bio [March 2007])
This is one of my favorite books for unlocking new discoveries in the city and I highly recommend it.