Originally Posted by kevmo911
Yes, that's an old SS-SS2-A.
is what you'd use to go from the tube fittings to 1/8" NPT. Any manufacturer that makes double ferrule compression fittings will have an adapter like that.
Also, that Harris 25-100 should work fine. You just need to remove the old nipple and nut and replace it with whatever cylinder fitting you use there.
edit - you'll likely need new ferrules. SS-200-SET
I am extremely grateful for your answer. There is no official Swagelok dealer so I'll have to dig around for the ferrules/adapter.
I contemplated the Harris (it was 20$ after all) but nobody repairs/rebuilds them in Kuwait and I found it used at a less than reputable place so I'll buy a Uniweld Co2 regulator instead.
Thank you once again.