The valve Alex refers to is from the "vm1000" series. The ram you linked is 8cm long, and so will be difficult to fit into an antweight design, but not impossible. Lego pneumatic rams will take up to 100psi with some modification, but you'll need heavier duty valves, tubes, t-junctions etc. than Lego ones.

As for tanks, the two most popular options are to modify a small aerosol canister, or to machine your own. Be aware that even though 100psi sounds like nothing in comparison to what the heavier weight classes use, it can still be very dangerous. Here's what happened when one of my custom tanks failed at 100psi: https://dl.dropboxusercontent.com/u/...2009.38.01.jpg. I could easily have been injured by flying plastic shrapnel if I hadn't been taking precautions.