@PPM
Hi, for your issue, please take the below answer.
All of our powerline kit devices contain one adapter, one or two extenders.
If you only want extenders rather than adapter, you can check if the single extender is available and you can buy a single extender.
For the customer in the USA, we currently only sell tl-wpa4220 single unit.
For the customer in the UK, the available single unit models in UK market are WPA8630P and WPA4220 and you can buy it from Amazon.
For other regions, please go to our official website to check. https://www.tp-link.com/home-networking/powerline/
If the single unit picture is available on the official website, there should be single unit sales on the market, we can use "where to buy" button to approach the retailers.
Hope it can help you.