Amazon has the DEWALT DCB201 20V MAX 1.5Ah Lithium-Ion Compact Battery (https://www.amazon.com/dp/B0052MIN3W?tag=quackdeals-20) for just $36 (originally $99, free shipping). This lightweight battery is perfect for powering your Dewalt cordless drills, lights, and other 20V MAX tools.
(https://m.media-amazon.com/images/I/51Q2Ig-Q3dL._AC_SL1000_.jpg)