I carried CO2 carts until I got a flat on the coldest day of winter and got stuck (i.e. the dispenser froze and it wouldn't dispense - between that and my frozen hands, I couldn't get enough pressure to the tire and ended up walking).
CO2 won't give as much pressure, so you'd need to carry a few of carts.

I'd go with a regular size pump, if possible, or a mini-pump if you want to conceal it.