i was in paris last summer, if your gunna be camping for the rest of the tour then you might aswell camp in paris, theres a sight about 20mins cycle from the arc de triomphe and its all through a park so its a nice ride. also the campsite has a free shuttle bus to the nearest tube station.
heres the website if your interested... its pretty expensive for a campsite but its still much cheaper than a hostel http://www.mobilhome-paris.com/en/default.htm
+1 it's also next to the 4km lap of the racecourse that a lot of roadies use for training. It's pretty close to central, and there's a supermarket not too far away if you want to avoid ripoff campsite prices.