Air pumps for the road need not be bulky or heavy. At right is my CO2 pump, with a quarter included in the photo for purposes of scale. It isn't difficult to find a place for such a pump for almost any bike. A bit of tube strung between the saddle rails would be enough to hold it. Just be sure that the pump head can be used with the type of valve your tube uses (Schrader or Presta). Some can be used with both types of valves.
The first time I used this, I couldn't figure out how to make the CO2 come out. It screwed in OK and then - nothing. It was only later that I realized you screw the cylinder in to the pump head and then, while it's on the valve, unscrew it a little at a time until the CO2 goes into the tube. The cylinder gets real cold when the gas goes out.
This is a great invention and a great use for Greenhouse gas. The only downside is you only get one shot per cylinder. Two if you're real lucky.