In answer to IO540's question the O2 fitting he is searching for a name for is generally a 1/4NPT thread fitting on american aircraft and and either a 1/4BSP or 1/4 Swage fitting in Europe. I have adaptors for those as well.....
The O2DT kit requires a first stage and the standard first stage has 4 ports with quick connect self seal ports. The MH oxysaver kits use flow meters and oxysaver cannula and these will plug into the ports. So you on a 4 port regulator you could have 2 people using the O2D2 and 3 people using oxysaver kits. In the even of a failure you switch to Oxysaver kits.
As far as O2 is concerned, if you take a Euro spec cylinder with a DIN477-9 fitting or CGA540 and a bullnose convertor to any gas station you will be able to get it filled for a couple of quid with the correct grade of gas. Linde Gas, Air Liquide, BOC etc. If you want paperwork to get fills from a SCUBA shop then I run basic nitrox courses, non diving just half a day in the classroom that will give you a cert to hand to a dive shop if they are really being that anal over filling. Saying that IO is the only person I know to have had a problem!
To fill a standard O2 bottle should not cost you more than a fiver anywhere which is 100 times the actual cost of the gas but will be covering cylinder rental etc.
Anyone who wants a fill is welcome to fly into me and get a fill while they wait for a fiver.
I hope that helps.