Operating semaphore signals

Hi All.   If I ever get around to installing Semaphore signals, can anyone tell me where I can get my hands on Memory Wire to change the position of the signal arm, a few year’s ago I built an O gauge junction signal with three dolls built from a drawing in a famous Railway magazine I even had the cheek to enter it in a show, I got a photo of myself in a Daily newspaper. This time it would have to be OO gauge though. Best wishes Kevin