Just spent 3 nights in Paris. I naively thought (I'm fairly new to GF) I could eat out providing I stuck to plain things like grilled fish and steaks. Not so. I came back more ill than I've been in a long time. We're not giving up on Paris - we love it - but cosy bistros are out from now on unfortunately. In future we'll rent an apartment and have meals in. Then hit the cafes for a glass or two.
A website I stumbled on all too late is very useful and informative on GF Paris, is
davidebovitz.com
And one baker I can recommend from first hand experience is this one. Good for lunch or takeaway.
Chambelland
Rue Ternaux
Metro: Parmentier
They do very nice focaccia style breads, and have terrific sandwiches and cakes etc. Open Tuesday to Saturday daytime and half day Sunday.