Here's the link. I now have 7 of these. Tried doing it all the ways mentioned and I found the best was mounting the ball directly to the little flap that you cut. Gives the most motion, it is the quietest and least troublesome for battery changes.
The new Weazel balls do not have the little push button on/off switch. It is just a little rotating cover that holds your battery into the holder. With this change, I found it easier to throw away the not motorized half of the ball and just mount the motorized side to the decoy with a #10 machine screw. Just be certain that the screw head will not hit the rotating counterweight as it rotates and you are good to go.
Also, the little cut flap will allow you to flex the decoy open to access your batteries about 100 times and then the flexing causes the plastic to begin cracking. Eventually I put little 3/4" narrow hinges on mine.