I have tried the LightWedge Paperback LED Book Light with my Cybook gen3 and in my experience it does not work particular well because of the size not the LightWedge is to big and the batteries get in the way.
The concept is promising, but a bespoke edition made for 6 inch ereaders / readpads is needed for this to work.
Edit: I use the
Mighty Bright XtraFlex2 DUAL SUPER LED and its works very good!