Hey there.
In my day job I am a materials manager at a major manufacturer of gas equipment hardware (O2, welding, cutting, etc.). A significant portion of our business is O2 clean valves, whips, lines, fittings, etc. for hospitals, EMT, and all, you know.
Now that you have the fitting types and hardware that you're looking for you're going to find that many, many gas supply shops will be able to help you. Oxygen clean is not a standard that is unknown in gas equipment supply shops (at least the ones without significant damage
).
If you're adventurous, you can get what you're looking for at many of these. You may well pay less too. I am not sure, but why limit your options. But there is that advantage of going through a diver-specific supply point in that they already have figured out this solution.
Either way, I just thought I'd throw in my 2psi.