http://www.pilotsofamerica.com/forum/showpost.php?p=732989&postcount=17

Go down to the dive shop (or online to OMS) and buy a 40cf LP steel bottle and
a low cost O2 clean reg set (All Scuba Pro gear is O2 ready from the factory,
get the cheapest Mk II first stage and whatever is cheap from them for a
second. You may also find gear at your Pawn Shop. You then attach a mask from a
CPR style "bagging" kit(most any medical supply will have them) You can be real
nifty and mount a $15 mic in it.

Instant demand O2 kit. Way better than any free flow system. Price depends. You
can probably pull everything off eBay for $200.

http://www.pilotsofamerica.com/forum/showpost.php?p=732655&postcount=3

Get a tank and transfer whip. You can get most everything you need from the
welding supply shop. O2 is cheap as chips, just follow the basic O2 handling
safety rules and when you transfer the O2, do it as slowly as you have time for
to minimize heating the fill tank so you keep as much pressure as possible
after the temp equalizes. Just keep oil and grease off your fittings and fill
slow and it's all good. I think Sporty's may even sell premade O2 whips.