In my part of the world, we have a truck driveline shop that builds and repairs truck driveshafts, and sell/services wet-line kits. 

He also does repair to PTO shafts on ag stuff too, and has a pretty good supply of the stock for the slip joints. 

If you can find something similar in your part of the world, need to take both halves to them so they can properly time the assembly upon repair...

Good luck.
Luke