There is only one mask worthy of persuit here and that is the optimask. They cost but are certianly worth it. You can use the mask, you can use tube and mouthpiece.......the versatility is just what the doc ordered.  Go to clusterheadaches.com and order one. Money is worth it, you get it back from not buying trex.
Edit........insurance would be more willing to pay when the optimask is perscribed, with a need for medical nessecity letter. 02 suppliers are required to provide perscribed breathing devices..been there done that.