Something else would be the
Gatewood Cape.
330 g without pegs!
It is a Tent which you can wear as a rain coat. Made for persons up to 190 cm.
It is existing in green too.
You could combine it with the 340 g Snugpack Special Forces bivvy bag, and the orange Decathlon pegs, 5 pegs fir 7€, 6 are needed. 6x 9g are 54g for the pegs.
Altogether with Raincoat Tent, bivyy bag and pegs 724 g. !!!!!!!!!
You can construct it with a nature stick (ore a pole or a trekking pole). I think, it is possible to hang it under a tree or a washing line too.
That's really light weight going!
The Dog should fit in the corner too.
But as a poncho perhaps a bit to thin in the forest. If you stay on the ways by using it , it should be ok.
It is ultra light trekking material.
Not so expensive too.