broken spring?

after moving to my new house my napoleon clock wouldnt work i cleaned it and eventually found it was out of balance and reset the crutch and all worked fine.
now the spring for the chime has broken i think. i can wind it so much then the spring goes free, i can feel the pressure loss on the key. if i am careful to not go too far then the chimes work ok.
i am obviously going to have to strip it again, but where would i get a spring from?