You can put a music wire/drill rod pin in for the small axle, but you will need a lathe and heat treat skills to do it. Of course, this assumes that the two axles were perfectly centered to begin with. If not, then the bridle may have to be bushed. Actually, as I think about it, it probably should be bushed anyway with a new axle.
If there are any other defects in the tumbler, then I think a new tumbler would be in order. However, if you make a new tumbler then a new sear might be necessary. When you start replacing with custom parts, then more and more needs to be done. It makes me tired thinking about it.