C-body help please

hello, got a buddy that has a very very very nice 72 imperial 440 car...no you can't demolition derby it...... It needs a new heater control valve / climate control valve which automatically switches back and forth from a/c to heat depending on inside temp... He cannot find one... He wants a new one or possibly have his sent out to get rebuilt...anybody have a website to where he can find one / order one...He knows they won't be cheap..

Chasduster