Finally something I know a little bit about....
There are high nickel welding rods that will stick to cast iron, but the weld is so much stronger than the base material it will usually crack beside the repair due to internal stresses.
A more permanent repair involves brazing with brass. The repair is about as strong as the base so it will last, but there is a concern about the brass' toxicity.
Perhaps the best option is to rivet a new steel handle on the stub and accept the new "style" of the handle.