Anyone have any clever ideas/product info for an easy to use lock on a trash bin?

We have large bins on wheels with flip tops provided by our city for automated trash pick up. One for trash, the other recyclables. Recently all the recycling rules changed so that only very specific things are now taken and to add things that don't screws things up along the way for all.

Mom has dementia and keeps busy emptying wastebaskets and at the same time I keep seeming to notice a disappearance of the lids for my lock and lock nesting bowl containers. So I'd really love to find something that would potentially perplex her but still be easy enough to release and let ME throw trash in when need be.

I know the folks up in Toronto..some may have some sort of turning knob that has to be matched up to keep the critters out. I don't know what to call what I'm looking for to even hunt for it!

Thanx in advance for any ideas!