Emission control components...

The question is where to get emission control components. Does anyone know of some vehicle that uses a small solenoid valve, about 1/4" or so port size?
What about a 2 PSI valve?
Details: I'd like to replace a "Rochester" valve used in a Jaguar fuel vapor vent system with something more reliable. This valve is designed a combination of a valve that relieves tank pressure greater than 2 PSI, allows relative free flow back to the tank under conditions of falling tank pressure, and allows unrestricted flow when the engine is running. The latter is detected by manifold vacuum. This is in the fuel tank vent line that feeds vapor to the charcoal canister. The problem is it's a notoriously unreliable device, and one is always uncertain if it's working.
I'm thinking about replacing it with a solenoid operated valve in parallel with a 2 PSI valve. The solenoid will open when the ignition is on. Otherwise, the 2 PSI valve vents tank pressure above 2 PSI, and allows free flow into the tank if the tank pressure drops below atmospheric.
So, where can I get a 1/4" solenoid valve and a 2 PS valve? I'm hoping someone will know of some GM year/model that I can search junk yards for, or step up to the dealer's parts counter with a part number.
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