Fodors recommends this booklet...as the bible for all parisiens...where to buy it?
It's a great map book. I bought my first one (about 4x6 inches) 20 yrs ago at a Borders book store. I special ordered a large one a few yrs ago from a local newsstand here. Last April, I bought one for a friend at a newsstand located on rue Cler in Paris. Paid 5 euros. If you can't find one where you live, pick one up at a newsstand/store in Paris. They're all over. I wouldn't go to Paris without mine.
I think I know which plan you're talking about. It's "Plan of Paris / District" by Plan-net. It's similar to London's A - Z guide. Its both in english and french. I bought mine - which I LOVE - off of ebay. I paid 12 bucks for it. It was "used" but looked brand new when I got it. The person only used it once and actually left business cards of the restaurants they visited in it. The ISBN on the book is 2851730525 (you can check it out on Amazon.uk)
The one I use is Paris par Arrondissement. It's in French but then, so is everything in Paris. It includes a list of the streets, squares, etc & then tells you what arrondissement the streets is in & the coordinates. Also gives you the metro. Each of the arrondissements is a separate map page. Really helpful in getting around.