I've made a couple of them, it's not hard if you can find someone who can thread the polycarbonate.
I think there might be thread buried somewhere, and I think Fhilo might be able to get some stainless required.
There is also a special fitting you can get that allows you to use a thermometer through the bottom fitting that I've used and is really effective. I have one around here somewhere I can show you at the MO, remind me.
JQ