Hi Keith: I would look for an Aires servo pendulum vane. Great unit, lots of them made. They steer like a champ. As to where to find one, that is a bit tougher. I would start with a "Google" web search for "Aries Wind Vane" or maybe "Nick Franklin" who used to build them. Monitor makes a modern version of the Aries in stainless, but they are going to be more costly and are no more functional.

I know they turn up from time to time as my daughter found one some years ago on a boat in Mexico and added it to her boat. Good Luck – Steve