Where can I find an electronic actuator valve for low pressure gravity fed drip irrigation?

"Bud" is on the right track; the valves used by automatic sprinkler systems are 12 volt and rely on a solenoid valve to open; they don't need any istance from water pressure to work. I use them on a low pressure system with a standard Rainbird controller and they work fine. The price 5 years ago was about $30 for the valves and I don't remember what the controller cost. Try Home Depot.