I went with that one (there was not much choice for 3rd gen anyway on the French site)
https://www.amazon.fr/dp/B07JKM6DZJ/ref=cm_sw_r_em_apa_koM9BbM8RHFBFThe whole thing looks fine but it's pretty massive compared to the Echo Dot 2 + wall mount.
I have mine hanging up (ie Echo Dot is above the socket)
Due to the weight of the Dot 3 and probably the shape of the socket, the whole installation slightly tilts forwards.
I had to insert a discrete tiny piece of cardboard below the base to set the mount perfectly vertical.
You might not face this issue if you plug it with the Echo Dot
below the socket.
Your mileage may vary depending on the shape of you socket too.