Hrm..... now that's something I hadn't thought of before. Of course, I'm pretty sure you need to be a certified open water diver to get a tank charged -- I think I've had to show my dive card when doing that if the shop didn't already know me.

Any of the SCUBA types on apug got idea on how you'd connect the valve on the tank to a hose with a standard compresser "squeeze and squirt" handle? It'd be nice not to have to buy an entire regulator rig just to do this, although maybe one could be found on eBay that has just the valve and the low-pressure part that attaches to the boyancy control vest.