Lowes has oxygen

n2diving

Most dive shops get around the Medical Oxygen issue now by using ABO grade (Aviators Breathing Oxygen). It's suitable for diving and, at least in our area, lower cost than medical grade (because of the reduction in paper work and documentation, not because of any difference in production and filling). The handling is essentially the same, because the expectation is humans will be breathing it. In a jam, (i.e. you don't care what it costs) you can also get it transfilled at the FBO of many airports, just make sure you have an CGA-540 to SCUBA fitting.

Genesis

I use ABO here; its readily available without hassles and is cheaper than Med-grade (but more expensive than welding)

Since its intended for breathing you obviously are either diving with it or using it in your light aircraft when you go to buy it. When I set up the account a few years ago they said nothing other than asking for the usual commercial-type questions (e.g. where do you want the bill sent)

The only issue I have around here with it is that if I don't call them in advance they may only have "K"s instead of my preferred "T"s, as they send a lot of the ABO over to the local air force base and as a consequence are often out of the "T" cylinders. Not a big deal other than the "K"s having less gas in them....

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