Hi Les.
In that case this one is the one I used when designing the app:
https://www.banggood.com/5V-ESP8266-...r_warehouse=CN
It will come from China so will take 2 to 3 weeks to reach you unfortunately. I don't see one on ebay, but Amazon has what looks like the same module:
https://www.amazon.co.uk/DollaTek-2-...206252&sr=8-36 at twice the price, but UK based.
You will also need a suitable 5V power supply and a box to put it in per the manual.
Cheers, Bob.