Little Silas needs a portable oxygen device

As most of you know, our 3 year old Silas has Hypoplastic left heart syndrome and Pulmonary Hypertension. He also has an undiagnosed lung disease that caused his lungs to be malformed, small, and constantly "wet". He's had multiple procedures, 2 open heart surgeries and also his 1st 8 months of life at UCSF. He was lucky enough to come home at 8 months old, still on Oxygen. He was slowly able to wean down and be completely off of it at 14 months old. His oxygen saturation baseline was pretty steady around 80-83. In the last five months his health starting declining. He developed a cough that wouldn't go away and also caught a virus. From that we learned he had pneumonia and was put back on oxygen after a 2 day stay at UCSF. He's now constantly hooked up to a machine, and has to be hooked up to a pulse oximeter several times a day to makes sure hes not in danger of another stroke. Whenever he goes to school or outside of the house, hes connected to 2 large heavy tanks on wheels with a 10ft tube. (Very difficult with a 3 year old). I've been fighting with the oxygen company and his insurance for about a month to get him a small 2lb portable oxygen tank that runs on batteries so he can be a normal active 3 year old again. His insurance FINALLY approved it but now we have another dilemma. The device is on back order with a waiting list since November. They have no ETA of getting the device. Could be a year. I just want him to be able to feel like a normal kid again even though he's attached to tubes. I found a portable oxygen concentrator his size but they don't take his insurance and we can't afford it. His dad had to quit his job to stay home with him so he can get the care he needs. With his oxygen, because of his heart and lung anatomy, he has to stay between 76-85. Any lower he could have another stroke, any higher and his blood could circulate back to his lungs. So it is very important he is closely watched. Please help me get Silas mobile again! Thank you