Portable Oxygen Concentrator

I am hoping to get a portable oxygen concentrator because going anywhere with two or three tanks of oxygen is hellishly hard. The one I'm looking at runs about $3000, and I don't think I need to tell you I don't have that kind of money to spend right now. I've looked into rental which would be covered to a large extent by Medicare and insurance, but that means I can no longer have a regular oxygen concentrator here. Insurance will only cover one, and the portable really isn't the best choice for 24/7 use (no matter what the sales guy says!)

Any help you can give will be very much appreciated. I hate asking but I hate schlepping all those tanks even more. If you can't contribute, no harm no foul, I still love you all.