I prefer sleeves than cases. And for the last few ereaders (kindle paperwhite, Kobo Aura one and Forma) I've used the one below from Etsy. The seller is from Seoul, South Korea and I give him the model and he custom makes them for me. I chose a darker exterior and without the logo. Amazing sleeves and very durable. Attached my Forma sleeve that I just received from them in a week. Would recommend and am sure there are other options as well on Etsy for Forma sleeves.
https://www.etsy.com/listing/4000346...ray-ebook-case