Back in the 70s a good mate of mine gave me a brand new Smiths 100PSI oil gauge still in the box, matches the stock gauges, but I never installed it and sits on my self in the shed, a few years ago I got my Norton gauges rebuilt and the shop they had the oil line kit to be able to mount it, just had to mount the gauge in between the tac and speedo I just made a mounting bracket, well that was about 15 years ago and it's still sitting on my self, I just thought after 48+ years without an oil pressure gauge so never bothered to hook it up, but it looks good on the self with all my other gauges I have collected over the years, I ran into my old mate a few months ago and told him I still have that gauge he gave me all them years ago.
So maybe find someone who specializes in selling/rebuilding gauges as most have full new kits that will look good, you never know you might get a new Smiths oil gauge to match.
You never know.
Ashley