This is thermowell is for my HLT. As cool as a nice SS one was it was overkill.
So I took the copper fitting (a compression fitting/ 1/2 MPT) drilled out the constricting part of it in the middle. This allowed the bendable copper tubing to come in from the opposite side. I took a piece of soft copper and bent it over a few times and banged it with a hammer to meld the one end closed. The other end was cut and cleaned up with a file to make sure it was smooth.
Initially made one with 1/4 " copper tubing and it worked well. Unfortunately the thermosensor I wanted to use did not work with the temp switch. The sensor that came with the Chinese temp switch was much thicker. I made another one from 3/8 soft copper.
It works great. If I used soft copper on hand total cost would be under $4. I was able to buy a foot of copper for under $3 for each size.