You can see a picture of the roll pin, or drive pin you need, go on ebay and search 'ferguson pto adaptor' .
You just knock them in with a hammer.
Your local garage or agricultural mechanics will have them, you might have to cut to the right length.
Also worth considering is replacing shaft to the bigger size as mentioned above, and or an overrun or freewheeling adaptor, stops the momentum of the implement pushing the tractor forward as you slow down.
Hope this helps
Regards stu