Little Keeper Sleeper Modification

I recently got a size 16 LKS and love how it feels; I am fairly flexible though and it's quite easy for me to undo it.

In order to make it more secure for me, I want to modify the snap panel at the top of the zipper, or the zipper itself to allow for actual locking.

Anybody have ideas on how to accomplish this?

There's locking zipper pulls you can get from YKK that you could replace the slider with. There's also the option of adding grommets by the cover, to make it lockable. You could also make a small hole on each side of the zipper while it's up, and loop a ziptie through and around the zipper.