Should you find another hammer, keep in mind that if it was fitted to another revolver it may not work in the one you have. This generation of Colt revolvers were intended to be individually fitted, and parts are not necessarily interchangeable. In other words, they don't simply drop in.
Perhaps some better news is that Colt D-frame revolvers made at the time, regardless of model used the same hammer. So, you can expand your search.