Congrats on your successful design! I've been endlessly contemplating something like this since I got my K3 but never had the fortitude to take on the project. I'm going to follow your lead! Last week I bought a Amazon leather cover from a guy locally that just sold his Kindle. The pins on this cover look to be identical to the ones in the photos of the lighted cover but painted black (They're metal btw and might actually be brass from what I can see from a scratch through the paint). I'm going to scale the photos here of the pins to what I have and if it checks out, I'm going to perform surgery on my cover.
I bought the cover for 20.00 in like-new condition and for a couple bucks and a bit of time, I think I can emulate the Amazon lighted cover or do better
In regard to side lighting via a sheet etc, I'd think twice about it. At one point I owned
a Sony with the built in side lighting and the added layer over the e-ink really messed up the contrast and added extra glare
Thanks again for your pathfinding! Any opinions on modding the Amazon cover are really welcome
All the best!