Just ordered off Amazon in pink for $20 plus Prime free shipping - a great deal!"Best" is always going to be a matter of what your needs are. I personally us a Black ful Ditty as a backpack for my iPad:
It's small for a backpack, but large enough to carry the iPad, charger, and some accessories. In fact, I can carry my 11" Air, iPad 2, and other items at once in it and it's still very small.