If the Onyx Boox M91 would be the winner, you could order him here, for instance:
http://www.onyx-boox.com/
They deliver worldwide, but I don't know if you feel comfortable ordering outside of Poland.
I wouldn't care about the battery time. I have my doubts that there will be remarkable differences between the devices. With the Pocketbooks you can increase the battery time by putting off the wifi and the accelerometer.
Yes, Pocketbook can read books, too, they call it "text to speach". On this site you can see in which languages they offer this feature:
http://www.pocketbook.de/support/pocketbook-902/ - Polish is amongst it.
Pocketbook uses the same DRM scheme as Onyx so you should be able to read protected pdf-files with the Pocketbook, too.