hi john,
ive made a few of my own to roy amesbury's design ME 1974. i think that's the only way you will get what you want without considerable expense from a 3rd party. i think ive read everything about miniature pressure gauge making in the SMEE journals and ME over the last 90 years!
not for the faint hearted, but very rewarding. i knew the late freddie dinnis whose FSD miniature pressure gauges adorn many award winning locos and were even used by Rolls Royce. i was privileged to know how freddie made his miniature gauges apart from bending the phos bronze bourdon tube (which he kept a closely guarded secret) – i had to work that out for myself! roy rather glossed over how to do this which is a shame. anneal, then burnish to work harden or leave to age harden.
cheers,
julian