TO-20 PTO SHAFT

Here's my story:
This tractor had one of the larger PTO shafts in it when I bought it. I managed to twist the shaft in two recently while bush-hogging. (broke in front of the Hydraulic pump!) I replaced the shaft with an old one with a smaller coupling and with an adapter to bring it back to normal size. Went back to bush-hogging. The adapter promptly twisted in two!
I did notice a lot of play in the adapter where it slipped over the small shaft splines when I assembled everything. I assumed the shaft was just worn.
Was this extra play the problem causing the latest adapter to break? Would this have been a poor adaptor? Or is there something else that may have been the culprit causing the original shaft to twist?

Should I buy just a new adapter? or the entire shaft? (conversion kit?)
and where from?

More info. I had quite a time getting the old shaft and bits of metal out of the hydraulic pump. Complete disassembly! I know I will have to rebuilt the pump & lift head soon but was hoping to use it until winter.

Any assistance is appreciated. Thanks in advance for the advice.

Larry Tillery in North Alabama