I also need white noise to sleep.
At home I have a simple one that plugs in and generates noise with fan. Looks almost exactly like this: https://res.cloudinary.com/guest-supply/image/upload/f_auto,...
When I travel I take this small portable rechargeable one: https://www.amazon.com/Machine-Babelio-Adults-Non-looping-So...
I'm on android so I don't have the built in sounds that iOS has
I use the mynoise.net android app. They changed it a few years ago, not for the better, but it is still servicable.