HatScripts
commented
2 years ago 
https://hatscripts.github.io/circle-flags/flags/earth.svg
Here is one based on the International Flag of Planet Earth by Oskar Pernefeldt (variant without borders) (2016)
- https://en.wikipedia.org/wiki/File:International_Flag_of_Planet_Earth.svg
- https://en.wikipedia.org/wiki/File:International_Flag_of_Planet_Earth_(Variant).svg
- https://www.flagofplanetearth.com/
I realise this isn't what you asked for—a flag featuring the continents of the Earth. I will likely add flags for the continents soon.
The way emoji handles it is by having a separate icon for Africa, Asian and the Americas:
pipcallas
.svg){kind=link}
Maybe someone has time to add a flag representing the whole planet. Something looking like a globe maybe.