I’ll measure laterYes you can get extensions but you need to know the barrel size (measured as outer diameter x inner diameter)
It looks like it could be a 5.5mm x 2.5mm which is quite a common size but you photos done show any kind of scale so I could be completely wrong.
5.5mm x 2.1mm is also quite common for screens and CCTV.
Just google something like 5.5mm x 2.5mm extension
It’s already going into a 4 way extensionHave you thought of a longer lead from the mains plug, it may easier to find
Find the size and polarity of the connectors and make your own if an uncommon connector system.
RS will probably sell them.
If you're lucky so will Amazon.
Or cut and shut the existing lead.
It’s plugged into one of those vanity mirrorsWhat plugs into the adaptor itself from the extension to the adaptor
Thanks, but it will be plugged into an extension lead. I am looking for a Extension for that little black plug.
A rough guess, 10ftAnyone with a soldering iron and a clue as to how to use it will be able to add in as much length as you need. As long as it's not a huge length, there shouldn't be a problem.