I typed in "Nevada, USA", checked the "public use" and "oxygen" boxes and when I hit search I got a map of Nevada showing airports listing oxygen services. I would call ahead to check.
How about a simple search for medical O2? Might be easier and cheaper...could be a medical supply house or similar...

This is a vexing problem and we are working on a database of airports with confirmed oxygen service. Part of the problem too is that there is no one available at the FBO to fill if it’s a weekend and the people behind the counter really don’t know at most FBOs. Best to try an industrial gas supplier like Linde rather than medical. Most medical O2 houses require a prescription....

A two bottle cascade is a great option at the hangar too....

Scott