Not to be rude, but anyone truly requiring the use of supplemental oxygen should not be traveling by airplane. Yes, the flight attendants have oxygen available for emergency use, but it is expensive to maintain and is not a passenger convenience item.

I would not count on power outlets on airplanes working, the technology is not consistently available and implemented, and even if the airplane has it, there could be aircraft swaps prior to the flight or it could be MEL'd (documented and repair deferred, as it is not a no-go item).