2011-11-24 I got a blue and a silver back cover for the kids last night at Best Buy for $1.99 each. The blue is very nice and the kids really like it. The instructions is in the box, very easy to replace.
Use the fingers to lift the back cover from the speakers slots.
Put the new cover back in, align with the top side (power button side) first then snap the bottom side (docking slot) to finish. Make sure it snapped in completely then slide the lock to lock position