@Fred_Flintsone They should sell an extension 9v cable,or supply a longer one. Then you would not have to buy a third party cable from Amazon and have to examine the cable and adapters specifications. I don't know how Tapo expect  a three meter cable, will be able to connect an outdoor camera mounted on an outside wall on the second floor, easily to connect power, with such a short cable. They must all live in single story houses. Certainly in the UK there are no such accessories available on the Tapo web page, in fact there are virtually no accessories available at all.

I was considering buying a couple of extra cameras but even though the cameras seem good for the money, look a little deeper and they become less attractive.

Fred_Flintsone wrote

The only reasonable way is to supply the cameras with one let`s say a 10Amp (10cameras) 12VDC power source.

Yoy can cable it in star or bus (or both) and convert it to 9VDC just before the camera.

To convert it to 9V just buy from Amazon a DC/DC Down step converter for each camera.

The converter is very small and you can put it into a small waterproof junction box just beside the camera, and cut a

short cord from the original power source to take the 9V from the junction box to the camera.

This way you have the mains and the power source where ever you want, and you take only 12 volts to the field/cameras.

This way the cameras are also isolated from each other.

One example of converter:

https://www.amazon.com/Magnolian-Efficiency-Converter-Supply-Waterproof/dp/B00A71E52G?th=1

This converter gives the camera stable voltage and enough current, and that`s all the camera needs.