I regularly use my CPAP for severe apnea. I did purchase the high priced Respironics 12v DC battery and case which powers the unit for 2-3 nights without compromising my on-board batteries (4) - 6 volt batteries in the MH. I know that I'm paranoid, but the unit works well in this configuration and I can use other on-board electrical devices without concern. I try not to use the humidifier on battery power unless absolutely necessary.
I just spent a month in Mexico and used an old CPAP machine with the humidifier removed. It is difficult to reliably get distilled water in Mexico, and there is usually high humidity so I don't miss the humidifier, and it is easier to travel with a smaller unit.
While traveling in Africa without reliable power I used a Z-Quiet oral device with moderate success. I also used an ear-loop surgical mask to increase the inhaled humidity. I carry it for emergencies.