You don't even need a fancy regulator. There are statically set units on Amazon that are about $40. They won't have a pressure gauge and will typically be set at 150 PSI. You could use an inline pressure gauge to allow you to check pressure without disconnecting the hose from the tire. I haven't gotten around to it yet, but plan to just buy a Co2 tank and one of these type regulators.
There are charts online that will give you a good estimate how many fills you can get on a certain size tank with a certain size tire. Just keep a running log of how many times you use the tank and running out of air shouldn't be an issue. I'll also keep a cheap air pump on hand as a backup. It will be slow, but I won't be stranded without air.
ben