Here is an older document from Resmed about battery requirements, good info. Most batteries on amazon are measured in WH, you can convert to AH with the calculator above and figure out how many hours of use you should be able to get out of a charge. Should be able to get close. Your mileage may vary

https://document.resmed.com/en-us/documents/articles/198103_battery-guide_glo_eng.pdf

Calculator https://footprinthero.com/watt-hours-to-amp-hours-calculator

battery https://www.amazon.com/dp/B0791WDZTW/?coliid=I3T1D20A8ZP9I0&colid=2Z0U1F795EW11&ref_=lv_ov_lig_dp_it&th=1

edit: need to get a DC/DC convertor to plug into cigarette adapter for most efficient usage something like this: https://www.amazon.com/dp/B07P6H994Q/?coliid=I190AAEUPB93CA&colid=2Z0U1F795EW11&psc=1&ref_=lv_ov_lig_dp_it