Not a regulator, Lee, just a pressure gauge for the SCBA tank. My SCBA tank has the exact one, which is why I'm pretending to be Phil :-). The tanks come with the gauge and valve, everything from the brass coupler on is the filling whip/station, whatever you want to call it. They're available multiple places, Joe Brancato, Mac1, PA, I'm sure there are more. You can also cobble one together yourself if you're willing to hunt around. Later.
Dave