First off a CO2 inflator give you limited air supply, if you carry 2 carts you "should" be ok, but if by chance you have a third flat your screwed. Plus you have to continually buy carts so the cost is never ending. CO2 is great though if you're racing and need to supply air fast.

A frame pump is the best, if your frame pump won't go above 50psi there's something wrong because even the worst mini can get to that pressure. Thus it may be time for either a new frame or a decent mini pump. Frame pumps are much faster and easier to get to high pressures, the best are Blackburn, Zefal hp, Topeak, and Silca Impero.

If you want a smaller mini style pump then there is a middle of the road size, in between a mini and frame pump in size, is the Topeak Road Morph G, hands down the best pump for the money in a smaller pump.

If you want a true mini, the best are the SKS Raceday, I have this pump too and it will get to 115 psi which is all the furthest I pump my tires up to anyways. Topeak has some smaller pumps that I've never used but do look promising like the RaceRocket HPX, but I've never used one so you need to ask around. Lezyne makes a very nice mini as well, but they are expensive, I have one and like it a lot, but I actually think the Topeak Road Morph is better for 1/2 the cost, but the Lezyne is lighter and looks nicer.

I will mention this, mini pump manufactures will say that their pump can reach whatever pressure, say 160psi...THEY CAN'T!!! Most mini pumps will only get to about half of that pressure! There are a very few exceptions that will get to about 2/3rds of the rated pressure, but none will get to the max rated. Also keep in mind that a mini will require around 500 strokes to get to 80psi, the Topeak Road Morph will take about 150, a frame pump about 60. Also I would try to buy a pump that has a hose nowadays, reason for that is because tube manufactures in an attempt to save a penny or two on construction are no longer reinforcing the interface between the valve and the tube, thus if you'r using a direct connect pump you take a risk of tearing the valve from the tube, although using the little stem nut on a presta valve will prevent most of that.