Hi Brian,
I think you are referring to this URL on page 4 of "Electrolyzers in the System Advisor Model (SAM): A Techno-Economic Potential Study:"
github.nrel.gov/wxi/sam-electrolysis.
Unfortunately, that is a link to a private NREL repository.
I did find this public NREL repository for an electrolyzer model, but I'm not sure if it is related to the work described in the paper:
github.com/NREL/electrolyzer.
Best regards,
Paul.