I searched this site trying to find the part number for a 3.0hg substitute for the Jaguar EAC-4371 vacuum switch, that has been recently mentioned here. I couldn’t find the PN, so I did the Internet research myself. A motorcycle vacuum switch made in the USA that is rated at 3.0hg is available from J&P Cycles, P/N #370-023. These switches can be adjusted for hg, and here is an explanation as to how to do it:
There are a number of these switches available for Harley Davidson motorcycles, and they range from 3.0hg to 7.0hg depending on the part number of the switch. I ordered the 3.0hg one as a spare.