Welding is the easiest fix. If you want to start a home business of extremely low volume, after it is welded, take it to a good jobbing foundry and get them to sand-cast half a dozen, using your repaired one as a pattern. If the foundryman is any good he should be able to cast the teeth, from memory I think they may have been sand-cast in the first place. You could have them cast in either aluminium or iron. I think I'd prefer iron, since there seem to be a few of them around that are either broken or have lost their teeth.
