Byrd's Oxygen machine

Byrd(JoAnne)needs a portable oxygen concintrator,which isn't covered by insurance..she needs a light weight machine to make her Independent and not house bound..she is on oxygen day and night..the Oxegen tanks are to heavy for her to be independent....help would be appreciated.... we're trying to purchase a Inogen G4 machine,which is only 2.8 lbs...any help would be appreciated...