Aqara have good door and window sensors too

Edited my post to include a link - someone used it for a bed occupancy sensor: https://www.homeautomationguy.io/blog/making-my-own-bed-sensor

Looks like an Aqara leak sensor. Zigbee - you generally won’t find Z-wave devices for this cheap. They were around US$15 on Amazon when I last bought some in 2023, and a dollar or two cheaper on Aliexpress.

Pretty basic construction. There’s two exposed terminals at the bottom, and when they connect electrically, it alerts. If you’re clever, they can be used for a bunch of things, not just leak sensing (eg https://www.homeautomationguy.io/blog/making-my-own-bed-sensor).

I assume you mean the date and time settings page. This is KDE’s one: