I've got a USB light but don't use it very often for two reasons. At first I'm afraid it could "break" my USB port due to leverage effects. Second it has 3 bright white LEDs and my girlfriend can't fall asleep while I'm reading in bed...
But I will give this on a try as it might solve both of my problems:

It's sold by a german electronics retailer called
Pollin, but maybe you find it in the US too...