Hey matey,
In regards to the butane cans, K-mart has a pack of 3 cans for around $5, all found in the camping/outdoor section

Hammer valves aren't exactly sold as product but are pretty easy to make with some basic hand tools. I've seen that video before and the guy has a few other videos building pretty similar stuff, if you have a look through, it should show more detail on his valves.
Basically, it's 15mm x 15mm male to male coupling with a hole drilled in the side. The bolts that are cut off are used as stem guides and somewhere for the spring to be compressed against. At rest with pressure in the tank, the rubber seal will press against the end of the coupling, sealing off the transfer port (side hole) from the air. When the valve stem is struck, it slides away from the end of the coupling allowing a rush of air from the tank to flow past the rubber seal and out through the transfer port. The spring and air pressure push the valve stem and seal back towards it's rest position and the valve re-seals.
It's quite funny really, i've just finished up a project based on the exact video posted

I'll get some pics up when I get the chance. Hope this helped out mate!