Although I can see why people like CO2 inflators, I've never been in favour of them myself.
When you puncture, before putting the new tube in, you should always find and remove the cause of the puncture.
If you don't, you'll just be stopping again a way down the road. Even if you've got a 2nd CO2 cartridge and some instant patches, you've got 2 punctured tubes, and no reliable way of finding where the punctures are without using at least part of the CO2.
If it's a thorn or a sizeable lump of glass, the cause is easy enough to find, but if you stopped because your tyre was down to 25 psi or so, the cause might well be something like a fragment of glass or flint smaller than the thickness of the tyre, and not readily visible from either the inside or the outside.
Trying to find such a small flint visually can take a considerable time, flexing each little nick open, individually. You may have to check the whole tyre more than once.
The hardest to find are generally fragments of wire strand (usually from the steel reinforcing in car/lorry tyres, I believe)
It's much quicker if you put some air in the tube, find the hole in the tube, and then line it up against the tyre, so you've only got a couple of inches of tyre to check (you did remember to keep track of which way round the tube was, didn't you?). The trouble is that a small, slowish puncture isn't that easy to find in a tube either. The best way is to just keep inflating the tube until it's several times the size of the tyre. The hole stretches proportionally with the tube, and the air leaks out faster.
That could easily use the whole of a CO2 cartridge, if not more.
A tube from a 25 mm tyre inflated to 2" across will use the same amount of gas as it would take to inflate the tyre to 8 bar/117 psi. I've had to take tubes to bigger than that to find punctures in the past.
I prefer not to be limited to the amount of gas I decided to bring, and rely on a proper Zefal HPx or Road Master Blaster pump.
On the subject of pumps, the basic rule is that the bigger the pump is, the better it works. That's why everyone with any sense uses a track pump at home.
Those "mini" pumps that work reasonably well (Topeak Road Morph, or Ajax Bay's Cannondale Airspeed) generally aren't very mini at all (a bit like BMW minis)