Reddit reviews Diymore 5pcs DS18B20 Waterproof Temperature Sensors Thermistor Temperature Controller Length 1M with Digital Thermal Stainless Steel Probe

I have a couple of esp8266 sensors. They are currently indoor, but your concerns about the enclosure wouldn't be a problem for them.

This is the probe I'm using on them. It's the same probe everyone else uses, but its for outdoor use. The cable and housing its in are heavy duty and weatherproof. Basically drill a hole in your enclosure, put the cable through it and seal it with epoxy.

As for power, mine being indoor I just powered them off a USB cable and moved onto the next thing, but I have seen a few designs for them that use batteries. What really kills batteries is using the wifi. If you put the wifi in low power mode, or power it down entirely, when not in use, it extends the life considerably. If you need constant, up to date readings this might not work, but if you just need to poll it periodically, this should work fine. If you needed every little temperature change, but didn't need it immediately, you could also have it continuously poll the temp, but only wake up the wifi once an hour or when the temprature changed more than x degrees from the last send, or something like that.

So I would need this

Sonoff TH16 Wifi Temperature and Humidity Sensor Switch+AM2301 RF Controller for DIY Smart Home,Wireless Remote Control Home Appliances and Work with Amazon Alexa, 1 Set https://www.amazon.com/dp/B075FSHKQ5/ref=cm_sw_r_cp_api_uZaZBbF8TQQ5Q

And the probe:

Diymore 5Pcs DS18B20 Waterproof Temperature Sensors Thermistor Temperature Controller Length 1M Thermometer with Probe (1M) https://www.amazon.com/dp/B01JKVRVNI/ref=cm_sw_r_cp_api_VZaZBbN6WY76M