they may take a while to arrive but aliexpress.com is a good site for thermowells i got mine along with a weldless kit and at the time it came to less than £8 although i think they’ve stopped sending via china post now so it’s a bit more expensive but have a look anyway.
This is my one http://www.aliexpress.com/item/19cm-Kettle-Thermowell-Kit-Stainless-Steel-1-2-NPT/32220936923.html its in a brewpaks FV and reaches from the Lid down about 10cms in the wort of a 20l batch, i needed a weldless kit as well.