go to Graingers if you have one of those around you. they sell little 8" air cylinders. my bro made on with one of them guys and a regular electric valve. it worked pretty well too
i build air actuated plates...but im having trouble finding a good, small, and inexpensive valve at the moment to keep cost and space down. Im shooting to have them sell for less than $225...hopefully.
price doesnt seem bad at all, would be great for everyone who already has air available. what type of valves are you using now? nice work though, looks really clean