Pedant alert: it depends where Clive is going
The foam in a can stuff works maybe every other time, if the can is new and the damage small. The way to have a new can of the stuff is to buy it as you go. For say the US where you can buy a can of foam at any gas station but recovery services don't do bikes these can get you to a tyre place. Bit of advice, ring the tyre place, some would rather come get your wheel than deal with the muck in the can.
Plan B is Ultraseal or gloop. Either put it in the tube before you leave home or after the puncture. Works (in my case) 12 times out of 13. Hole number 13 was where the nail found the tube seam and make a V-cut too big to seal. The French-Polish tyre fitter cursed the stuff in at least three languages but we were up and running in a couple of hours.
The 100% method is the tube change. In Mongolia, France or Salt Lake City on a Sunday, the UK if anyone is having a day as bad as yours etc. this makes you self sufficient and free of the limits imposed by supply chain managers. Change the tube, patch the one you burst when you stop for the night and repeat until the shops have stock.
A tip about tyre levers: it's not the size it's what you do with them
Practice, practice, practice until you know what your rims are like. Some (MZ, Triumph) can be changed with a pair of T-spoons. Others (Moto Guzzi, F650) need heat, lube, a G-clamp, two prop forwards...