The best I've found(for those of us who need glasses to read the tiny bus map on the back of the metro cards) is the Guide de Autobus Parisiens, a 4 x 8 paperback pocket guide that shows the bus routes posted inside Paris buses, with 2 facing pages dedicated to each route. I went looking for this when I couldn't find stops for return trips---they are never on the other side of the street from where you descended. You can buy them for 7E at the Metro store in the Les Halles RER station.

If you don't need it immediately, I can bring one back next week and mail it to you. Let me know.