definitely get an inflator that can use the non threaded 12g co2's, that way you can get them for cheep from walmart or any sporting good store for cheep.
I have started carrying a small frame pump as well as my co2, that way I will never be without air, even if I have to work for it.
this...

Plus this and 2 12g's = good to go.
When I get a flat, I use the pump to put a little pressure in the tire and make sure the bead is set, and there is no leak, than I use the co2 to bring it up to pressure.
I run 23's and using this method, I get the pressure in the tire up to 100+psi no problem.
ooh and I have a small seat wedge that holds a tube, the inflator above, an extra co2 (2 total) 2 tire levers, a small screw driver, and 2 allen keys. and works very well.