Another recommendation for the Topeak Road Morph... I usually carry two to three CO2 cartridges and a micro-inflator, but for long rides, centuries, and tours, I like to pack along my Road Morph. The bracket that comes with it can be zip-tied under your top tube, or you can mount it underneath a bottle cage. I've also had good luck just zip-tying the thing to my rack when I've misplaced the bracket ;-)