hi lori
these Coleman propane 16oz tanks are readily available in hardware, grocery, etc
they are 8” high, 4” diameter
https://www.walmart.com/ip/Coleman-Propane-16-oz-Camping-Stove-Replacement-Fuel/20971271
perhaps these, along with an oxygen concentrator, would be the solution you are looking for
(this concentrator is photographed with a slightly taller sized propane tank…)
julie