...try the search function here and ch.com for emgality et al...mixed bag but worth a try ...especially if covered by ins or coupons...
...there are whole sections on mooshies...check the new members banner above and member only forums...
....the "price" I paid sclepping O2 to work (e tank/cart) for 25 yrs, when in cycle, was the best investment I ever made...saved sanity, perhaps life, and enabled a job and career. When traveling arranged for delivery at destination multiple states/locations. Fortunate that it worked 70-95 percent of time greatly aided by caffeine/energy drinks ....100 percent with Zomig NS as abort of last resort.
.... extremely important to have proper non rebreather mask, enuff flow (15-25 lpm recommended.... but really individual) and proper technique (also highly individual dependent and based on trial and error)
...have you considered the D3 regimen?
Best
Jonathan