I asked a similar question about a month ago. One of the recommendations was for the Xiaomi temperature sensors (around ~$10/each). But there was some concern over their update frequency and I’m holding out for them to get native zha support in HA so I don’t have to buy yet another hub.
I have a bunch of old Zigbee PEQ/Centralite sensors that do two functions, temp plus door/window, leak detector or motion. You could hang them with a short piece of wire or stick a sheet magnet to the back.
Or go DIY and build your own for total control. MySensors is one such platform that’s supported. A bit of a learning curve there, tho…
I am using a wireless 433MHz temperature and humidity sensor from aliexpress, with an RTL-SDR compatible receiver. It’s cheap: 10$ for the receiver, aroud 5$ for the sensor, but you are limited to 3 sensors.