Agree with others, you don't need a new valve assembly, just the fitting to adapt the fill line, which can also be used to then fill the guns. Also good to have a gauge as well. You can upgrade to a regulated valve system if you choose, but I never have. Regs add some complexity but are arguably safer when it comes to preventing the accidental overfilling of a gun. Foster fittings are best for connectivity in the airgun world. Link below to an assembly from Brancato that I use in addition to other similar ones.
FWIW, the Scott valve handles are by far the worst to use, IMO. They have a slip clutch installed that tries to prevent the operator from accidentally closing the valve in operation. Great for firefighters as designed, but not great for airgunners trying to control the flow. So perhaps look at replacing that handle or simply removing the slip clutch. I just replaced the handle with a $5 faucet wheel from Amazon (1/4" square hole for mating). MSA valve handles are much better and are what I have on all but one of my SCBAs.
https://www.topgun-airguns.com/product/scba-hose-assembly/