In the past I have hired a Medistorm battery from Hope2Sleep (cheaper hire available elsewhere).
I use a ResMed AirMini for travelling (long-haul) and a AirSense 10 for daily use.
I recently got an USB-C adapter for my AirMini from Australia. It is supposed to work with Any powerbank over 45W. I purchased an extra powerful Anker powerbank (20,000mAh, 140W), so it is flight safe. This power bank has pass through charging, therefore theoretically it can be left permanently plugged in and used as an UPS in the event of a power failure for CPAP. You don’t need to do anything!!
I can just about get 2 nights sleep (8 hours each) out of the battery. My pressures are around 18. The battery recharges in just over 2 hours with 45W USB-C charger.
For me it was a much cheaper solution to buying a Medistorm battery with 1yr Warranty!
The USB-C (PD) power banks can be bought relatively cheaply off Amazon or Suchlike!
The same USB-C adapter can be used for the ResMed AirSense 11 (for daily use) soon to be Officially Available in UK. BTW: there is a different USB-C adapter for the AirSense 10.