If you want do a bit of DIY, there is plenty of solution.
One solution is using DS18D20. There should be waterproof version.
You would need an Arduino to read the sensor. You can take the route of Hubduino to get the data to Hubitat.
I personally make my Environment Sensor that is expandable. Coincident over the weekend, I build one probe using an ST32 Arduino. I am testing how long cable can I use. I tested 15 feet cable without issue. I am planning to see if I can get all the way to 100 feet.
I wrote simple child DTH and Arduino sketch for it. Please feel free to reach out if you like to pursue this route. Here is how it come out on the hub.
If you notice, there are many pin on the Arduino. Those are available for other things that you want to monitor or control.
Thanks
Iman
