Hey! I carry CO2 cartridges!
They do cost a bit, but i've had one? puncture in the last X years - so i can't recall what they're worth!
What is handy tho is that they're tiny and sit in my bike saddle bag - just in case!
BTW, i started to use these back when the smallest mini pump wasn't all that mini. So you ended up 'forgetting' to take it with ya. Now, Crank Bros have brought out totally microscopic pumps that can be bought on ebay for peanuts!!
I hardly ever need to use a pump whilst riding now, track pump at home is way easier. But, if I did get a flat... (which is why CO2 is good, just chuck it in ya saddle bag and forget about it - but not the valve bit!!)
I've found that the best bit on the CO2 cartridge valve thingy is the presta to schraeder adapter!
I reckon service stations are great as a backup! AND they usually have things to fix a 'flat' rider too.
Also good are bob jane's tyre places, garages etc.
BUT! learn how to be self sufficient and don't rely on others. Also, CO2 only lasts once - two flats and you're out!
(Disclaimer to those who think i'm promoting complacency)
Back to the topic - best servos? They all put out about 50psi+ so it should be sufficient to get you to your closest - home, buddies' place with track pump, LBS etc.
To be honest tho, the gas station pumps are pretty inaccurate pressurewise. I'd be worried if i pumped up a tyre to around 100psi...maybe it would be 80, maybe 130?? Considering i'm anal about tyre pressures and check pressures before every ride...