Where do i find a stepper valve?

the stepper valve is fitted on the throttle body it is a round black thing with a multi plug attatched which has about 6 wires in it the motor is secured by 2 small scews probably 20 torx sometimes removing an cleaning carbon deposits can sort problems out with them after that try initialising ecu by disconnecting battery for 10 minutes put back on and start engine turn on rear heated screen and headlights leave to idle until fan comes in then drive for 45 minutes driving using different styles high revving etc this method usually improves how the car runs and drives hope this helps