Here is a link: They have a LOT of valves, metal, plastic, etc.
This is the one I use and recommend.
Get the THREADED one for easy assembly, repairs, and recycling.
57200 1" FNPT Auto Inline Vlv NFC; B
They will ship from the factory and customer support is GREAT until you mention we are using it for paintball cannons. So don't.
This one is rated 150 psi water and many other sprinkler valve are rated only 125 psi water and they don't print the rating on the box. Just have to ask the factory.
You will notice that little black flip lever just to the left of the black solenoid on top. That flips 90 degrees on and off manually. I used that lever for YEARS and never hooked it up to a battery. Used that solenoid for a handle and used my thumb and index finger to flip it back and forth.
Index-down-fires. Thumb-up-closes the valve and recharges the air chamber.
The NEAT part is you don't have to modify the valve in any way. Plug and PLAY upgrade for your cannon. A screw together plumbing project. Runs about $22 but have seen them on their website for $12 in the past. I also happen to have two brand new ones for sale. (cheap)
I went to all metal quick exhaust valves in my RPG and Tank Cannons. Costs $40 plus another $12 for a shop air valve for a trigger. 300 psi rated Fire extinguisher body for an air chamber and have beat it up for years on the field of battle. Very safe, Very reliable, no repairs - just cleaning. Let me know if you want to go that route. Both Auto-Refils the air chamber while you are reloading a Nerf in that sliding breech. It will be ready to fire before you can get it reloaded.
Pic below is my current beast but used the SAME configuration with that sprinkler valve for years.
20 inches of trouble for anything with walls..An anti tank 'side arm'.
I share all my stuff. Take pics of what I do. Have a HUGE library of failures and quite a bit of stuff that actually worked. So don't ask me for "All" of it. (you don't want it) Narrow it down and pick my brain and tell me what you want to build. Happy to walk you through a build.