Lil Me....I'm wondering if a clapper is what you really need. If you're falling asleep while reading, would you not fall asleep so you could clap? If you're conscious enough to applaud before falling asleep, you'd be conscious enough to turn the light out.
I don't know if this would be any MORE helpful, but hubby got me one of those adapter things that plug into the outlet that turns any lamp into a touch-on, touch-off. (for the very same reason) You barely have to move.