I have used DeCal Girl skins for my Kindle Oasis before. They are good quality, and come in lots of different designs - you can also supply your own image and they will make a skin using that. Easy to apply, and easy to remove also. I removed mine after some months because I wanted to go back to my original color.
Only thing to watch is they will cover the front and back but the side will be exposed.
I don’t know which Kobo you have, but here is their page for the Kobo Libra Colour:
https://www.decalgirl.com/collection...a-colour-skins