It might help to know where you are in the world.

I initially had trouble getting an O2 prescription at all. Once I did, most of our local suppliers wanted me to sign a contract to deliver O2 every month whether I used it or not.  Since I am episodic, I decided that's a total waste.

One of our local medical O2 suppliers agreed to sell me a tank for US$100, and they charge US$20 for a refill, so I went that route.  They also had the regulator and mask I needed, but they wanted US$250 for the pair.  I bought a regulator on Ebay for about US$25 (free shipping in the US) and I bought the clusterheadaches.com mask which was also a bargain.  This was all well below my insurance deductible level.  You can make a mask that will work well until the mass produced one arrives.  This site has instructions if you look.

Welder O2 is another option.  You don't even need a prescription for that.  There are also tons of posts on this site about how to do that.

We are in the United States and our local fire station is volunteer so it is not manned round the clock. Tomorrow morning we will be camped outside the dr office when they open.  Oxygen is a must have.