Fill flash helps alot when shooting green screen (or anything else for
that matter. These little fill flash units are absolutely perfect for
home photographers! They take 2 AAA batteries, have a reasonably fast
slave trigger (they go off when they see the flash on your camera go
off) and are very compact (see drawing).
At only a little over 3/4" deep, they're
easily spring clamped onto various stands. I've even fastened them on
the back of a subjects belt to give a nice uplight/backlight fill.