http://23.94.143.123/kindle/kindle_header.stl
As for buying batteries it was around £15 I think, which is more than you can buy a faulty k3 for (7-12 quid).
I was running one with a drone battery in for a little while, which did work but was flakey again. Wouldn't choose that for a kindle I wanted to take places with me, but if you're after using it for a weather clock or picture frame etc, then a usb powered setup will work
This is my use case:
https://youtu.be/1u91N8Ai91s
The two larger frames here are to mask the keyboards from k3s, and both are using this external usb cable for power