Mine is an Armval, but they dissapeared some years ago. Would be quite easy to make one though, it's only a non return valve with adjustable spring pressure, when the boost reaches the required pressure it lifts a ball bearing off it's seat against the spring and the pressure can reach the actuator, when the boost drops again the ball seats and a tiny bleed hole lets the wastegate return to the fully closed position.
Something you could knock up after tea Barry.