Looking for the same thing. I have one I love right now, but it will die and I will never buy a non self repairable ereader again.
https://www.crowdsupply.com/diptyx/diptyx-e-reader
This is the best one I could find, but I think the dual screen design choice is plain wrong. I also like my screens a bit bigger and higher resolution, but on those issues I could be nudged. Not the dual screen design though. Although having options like these will pave the road for our next options :). Good luck with the diptyx, Martijn, (and you on your search for your next ereader)
We had a very hefty book.