A much simpler approach than the previous one.
Let's use a brass thermowell, which will be compatible with our copper collector and its copper or brass connectors.
Brass thermowells are somewhat less common and harder to find, but they do exist.
They can be found online.
I found one at a very good price at a store called "Salvador Escoda."
Salvador Escoda brass immersion well
Photo of the thermowells on the counter at the Salvador Escoda store in Seville: