You can buy boxes of moldable foam earplugs which can do very well for noise blocking. Individually wrapped in pairs. They carry well in a back pocket. Those work if you’re ok with the sensation of something in your ears, don’t have ear tubes, or some other contraindicated condition.
An aesthetically pleasing pair of full muffs can also work. Sometimes kids need their environment dimmed, and the muffs can work rather well.
We actually already have hearing protection headphones for the kids, but they’re bulky and I usually don’t want to risk them getting messed up in the bathroom on a trip
We try to balance both giving her the tools to be successful but also not having her entirely rely on the hearing protection as a crutch