25 year sufferer of CH here... O2 is the only cure I've ever had. Thanks to a willing general practitioner I met 10 years ago who wrote me a prescription and worked with my insurance company, I was able to discover how wonderful it was. She has since moved away and my CH have gone away and come back, and it is a bit of a hassle to try to find understanding and knowledgeable doctors willing to help. The first thing they want to do is prescribe migraine drugs that do nothing and sometimes make CHs worse.
CHs came back last week and rather than bothering with the prescription/insurance/rental route, I went on craigslist and found several affordable resale oxygen concentrators for sale. I'm one of the fortunate ones that have found success with O2 concentrators. 10-15ml is ideal, but they are expensive. I purchased a 5ml concentrator today and have already used it with success. I have a technique that I use that cures my CH even with lower ml rates. My advice is if you can afford it ($250-500), try CRAIGSLIST.
hope you find CH peace.