I've never puchased from Power-Aire, but they have everything and their prices are not that bad. I have heard their name mentioned on here before. Have you also looked on Ebay ? I have bought in bulk from a supplier there with good luck. I'll try to find their name.
Thanks dadgonemad there is a HF close by for that price I'll have to pick a couple up and try them.
Diabolik, this one from speed air looks great especially the push in connectors Union Straight - O.D. Tube 1/4 and at $5 each its not bad. Don't know what the difference between speed and flow control is though.
Fright the ideal size would be for 1/4" od tubing push in connectors would be nice but not required just make things a lot easier.
the speed control will give you full speed in one direction, but then will restrict your speed in the other direction (ex. a trash can pop up prop that you want to jump up quickly, but then go slowly back into the can without slamming) a flow control is going to restrict your speed in both directions.