I just checked CPAP power consumption. 60-90 watts. You can buy a SMALL inverter for few $. Do NOT get a larger one than about 175 watts or so. Reason? A small inverter will power your CPAP from a 12 volt outlet typically seen on boats. Anything larger could overload that circuit (usually 15 AMP maximum) and blow a fuse.
Which you may not be able to find or replace.
This size of inverter is also great for charging cellphones.
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