If i can be attached to mains then i would suggest you look at Hubitat with Homemade Temperature, Humidity, Pressure and Light sensor
I have had his sensors before and it worked well. I used it to automate a humidifier in the winter and it seemed very reliable. The only possible issue is does he have any available now as he makes them in batches. Only downside is that it doesn't really have a case so it isn't the prettiest device.
The secondary benefit of it is that it seems to function as a good zigbee repeater.
