You may be able to get the existing shaft fixed by cutting off the ends and welding on new shaft halves. If you don’t have the skills a drive line shop may be able to do it.
see this link for details
Shop Weasler PTO repair shafts & tubes for durable, precision-engineered performance. Fast shipping & guaranteed quality for tractors & agricultural equipment.
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may be cheaper to just buy the whole thing if you can figure out what ends you need. I imagine there are a few different types to choose from.
PTO shaft assemblies from Agri Supply® can help you complete your PTO shaft with replacement parts or get a full new PTO shaft.
www.agrisupply.com
you may be able to find the correct information about the shaft in the implement’s owners manual