Most solenoid valves will come with female NPT fittings, you will need to get the appropriate PEX adapters.
What you need to know when shopping for solenoid valves:
-Size? (sounds like you want 1/2")
-Normally (not energized) open or closed?
-Voltage? Most agricultural/irrigation solenoids run off 24V, the problem with these is that you need to use a 24V controller/timer or a separate 24V power supply. A 110V/120V solenoid would be more versatile, but you can't pick them up at your average hardware store.
Pictured is a 3/4" (bushed to 1/2") ,24V normally closed solenoid with a vacuum breaker.
Here's another solenoid valve, this one is a 3/4" valve (bushed down to 3/8" compression fittings for PEX supply tubing) with a power supply attached, I use it with a digital timer to water my wife's flower baskets.
You could try calling industrial supply firms in your area..graingers has a web site, mc master-carr as well..only options I can think of, if you must go with line(110vac)voltage
I don't know how you want to go about "switching" the solenoid.
Its the solenoid is going to be NC than I am guessing it might be for water changes or something that does not require continuous flow so you don't have to worry about it being Brass or PVC
Talk to John at JEHMCO. I got my solenoids from him for the drip systems hooked to my tanks. The brass one to the left of the filter bag attached to the back of the stand in this picture is 110v, normally closed. All I had to do was attach a power cord, and plug it in to my power strip.