Anyplace that sell Predator cues will have the shafts and some ebay only companies also.
This is where I have bought most of my predator shafts in the past and they have been very helpful and prompt to correct any mistakes that have been made. Also, very good prices.
I saw a post by Joe Rogan in one the threads mentioning he was using them. Apparently Predator is marketing them specifically for player from Taiwan which I found a little odd.
This is what Predator says on the site linked below...
Introducing FAT Shaft, designed exclusively for Taiwanese professionals by Predator. It uses the same technology as Predator's 3142 shaft for best-in-class accuracy. But with greater thickness and a stiffer feel, FAT Shaft will enhance your performance Taiwanese-style.
Well I may have been wro.. wron.. wrong about that site having the shafts. Go ahead and give them a call and see if they know what they are and how to get them.