The very best cheap pocket map you can get for Paris is called "Paris Pratique par Arrondissement" which you can buy at any news stand. It makes navigating the city easy, so much so that one can imagine that the introduction of such map-books might be part of what made the arrondissement concept so popular in the first place.
Google maps are great but they don't have the schematic version for Paris.
Here are some great schematic map I found on internet.
Visit Paris map for more info