I received today this cover
https://www.amazon.fr/dp/B01M1IEE51/...81_TE_3p_dp_i1.
Mind it is NOT a sleep cover - I don't use the sleep function. It is very confortable while reading, but it weighs 146g, so I prefer to read without at home and I find it a bit difficult to separate the reader from its cover: I manage pushing on the hole for the off/on button, but it is not ideal. I hope I learn to manage it better.
EDIT for the Noreve cover owners: how heavy are they? More than my 146g? If all pop free easy like Sweetpea's, and it isn't heavier than mine, I might invest in one.