Co2 chamber

I just bought a co2 canister and what I thought was an adapter valve that would allow me to put 5/16 tubing to the canister. I saw a few DIY chambers and most people weren't using regulators but $2-$3 adapters. What is this actually called and does anyone know where I can buy one? I dont want to go and buy a $60 regulator if I can use a $2 dollar piece.

I was going to use dry ice but the rat production is too sporadic for that to be feasible.

What about a valve from the hardware store? There is no pressure to regulate only the amount. Im in the process of making a chamber and using water valve

I use this:

http://www.amazon.com/gp/product/B0026OU454

Thanks for the suggestions. I was looking around online and came across a regulator for a really good price and speaking with a few welding places around here they told me that with what i'm using it for that would work well because the co2 tank would last me longer regulated. It was $40 but hopefully it'll be worth it. Even if I don't save any money with it the thing looks pretty cool so I could possibly use it on a home brewing set up if I ever go that route.