Ah, that's a shame. I think removing and inserting that HV cable is the single most difficult part of restoring Predictas.
It's unlikely (but not impossible) to find a replacement flyback given the demand. I suggest you attempt a repair. Get yourself some Super Corona Dope to paint over the repair and cracked wax coating.
Nothing special about the HV wire. Get some rated for 25kV or better.
Could be someone cut it to make pulling the chassis easier rather than trying to pull it out of the socket.
I've posted a ton of videos about restoring these sets that you may find useful if you haven't already seen them.
Tips:
https://youtube.com/playlist?list=PL...F5K780eNgJfybB
A series of 21" sets with chassis like yours:
https://youtube.com/playlist?list=PL...FeyZNmXLktdYHm