So my pressure gauge has never worked on my RODI (BRS system bought used). Was looking at replacing the gauge. I see a bunch on Amazon. Are any of those ok for this application?
As mentioned glycerine filled is ideal but plain old air filled work as well. You should just be able to unscrew the bad one and buy a new one to screw on.
BRS, salt water aquarium, spectrapure, and of course Amazon all carry replacements.