I am not sure your application but be very careful with high pressure equipment there is a very good reason that scuba tanks are filled in a concrete enclosure.
This is a fairly low volume/low energy application. I am guessing we are talking well under a liter of volume.
For background: I wish to build a cryo-cooler. Effectively, I want to replicate a Linde cycle gas liquification system http://en.wikipedia.org/wiki/Hampson%E2%80%93Linde_cycle
. While it requires high pressures, we aren't talking more than a meter or so of fairly .25 to .5 in tube.