I prefer a CO2 inflator over a hand pump because it fits easily in my seat pack and is quick and easy to use. I know I'm limiting how many tires I can fill on any given ride, but I've never needed more than two cartridges at a time. I carry two CO2 cartridges, a spare tube, and a multi-tool in my pack. That's pretty much it.

I have the Inertia Designs Trail Wedge which has been doing the job for a long time. It also comes in an expandable version if you want to carry a little more.

See both here: http://www.workbycycle.com/store/ind...oduct_list&c=9