My first thought is to wonder what has happened to that cylinder?
Are they marks on the neck? Bad picture? Gougues in the neck?
Assuming the cylinder is sound, and has a decent life still, then pretty much any HPA gauge.
Reputable airsoft shops that do HPA or paintball shops will generally have a gauge
The gauges thread will be standard (as long as the gauge is intended for an HPA cylinder on the high pressure side) at 1/8” NPT thread
You want the dial to go up to the bottles pressure, so assuming it’s a 3000psi aluminum then you can put on anything from 3000psi to 6000psi
If it’s a fibre 4500psi then I’m more concerned about the neck, and you would want anything from 4500psi to 6000psi
(You need to stop filling at the appropriate level so that means if you fit a 5000 or 6000psi gauge then you must stop long before the red)
I’d say to call your preferred retailer and ask if they have gauges
eg Super5ives don’t list them, but Chris is a good first call as he has a background playing in both airsoft and paintball
https://shop.super5ives.com/shop/category/8-air-co2.html
https://www.justpaintball.co.uk/search?type=product&q=*Gauge*
When you add the cost of a gauge plus postage you’re pretty much at half the price of a new bottle itself
Avoid unknown random gauges on eBay or from China etc
…. and if you do change it ….. drain the air fully !!!!!!
Ideally fit to a remote line and leave it open
