Garbage disposal stopper-strainer

I recently [remodeled my kitchen](https://beesbuzz.biz/blog/?tag=remodel) and as part of it I went from a two-basin sink to one basin. Which means that now I have just a single hole in my sink, which presents a challenge when washing dishes: how do I plug the hole in such a way that when I remove the plug, small stuff doesn't fall into the garbage disposal?

All of the commercially-available sink strainers I could find either weren't designed to work with a garbage disposal, wouldn't allow for a stopper on top, or were too big for the sink hole. So I decided to make my own.