The pressure regulator used for setting and maintaining the Generator Hydrogen Seal Oil Pressure (often referred to as the Seal Oil Differential Pressure Regulator) is a typical single-stage, spring-loaded pressure regulator, of which a fine example can be found at www.wikipedia.org by searching for 'pressure regulator'.
The only difference is that this regulator is rated for use in a system that has hydrogen gas pressure.
There should be some information about the regulator in the Service Manual provided with the turbine-generator.