Just go to Home Depot and buy a fifteen foot spool of cheap link chain for under ten bucks. Snip off six or eight inches (however much you need) and use that if you don't want your zipper moving.

In the video they also tighten it so much that the handle is folded over. If you do that to your bag and somebody lifts it by the handle, the zipper pulls will be taking the weight and you may not want that. Get a loop of chain, and that's not an issue.

If you don't like the look of chain, you can get aircraft cable loops (like they use for key chains) and attach that to the handle to secure the lock and zipper pulls to. Six inch ones are like $3.00, and a drop of crazy glue when securing them makes them permanent, and once attached to the bag you never lose it.