End cap when permanently removing sink pop-up

Are pop-ups required in bathroom sinks?

Are pop-ups required in bathroom sinks?


My bathroom sink has a sink popup whose stopper is missing its top round part (the top screws on compared to the popup stoppers with permanently attached round tops that I usually see in stores).

Anyway, I hate popups so I would much prefer to just have a stainless steel strainer in my bathroom sink.

My question is, are the popups required in bathroom sinks? I'm in Illinois. I would like to remove the stopper, the horizontal rod and replace the retaining nut with an end cap (if I can find one that fits) to seal the hole.