Couple of potential options:
M-Edge eluminator2 - I have the shorter one for the smaller Sonys. Brightness is just about right and if your reader won't flop away from your cover, it will still work. the attachment is a bit flimsy, though -- IMO, the light is great but the injection molding was poorly done. I've got a metal lined cover and replaced my clip w/ magnets -- most people don't have that option.
LightWedge Verso Arc-Light and
LightWedge Verso Wrap-Light- I've seen these in the store and by specs, this looks like a perfect lights - small, rechargeable, good lifespan and clips to most anything. LightWedge also has a good track record with their lighting solutions. Two catches: No Idea how bright they are and Oh-Boy they're pricey ($40)!