I said you can buy one, I use a small Victor oxygen regulator on the 250 psi tank and have a few used nice chromed L-TEC two stage ones in my shop for nitrogen and oxygen. And those $50 regulators are rated for 2200psi for oxygen and can be used with nitrogen or argon, just change the bottle fitting.
If they start to leak, and every one of them will no matter the price or maker, just replace them as it's cheaper than getting a brand name one rebuilt. And they will all leak eventually, the bigger problem is most welding shops in the US won't rebuild any of them.
They won't rebuild them because of the liability however, if you bring them in to adapt or change the fitting, no problems. Never had one that needed to be rebuilt but then again, they would not of got a lot of use from me. One used commercially may be different.
I just use medium, smaller and even smaller brown glass bottles with some plastic bag material below the cap. A batch mixed early November last year worked fine this week, replenished as per Kodak's instructions.