The ChugPlug by Lenmar has a 4000mAh battery adding up to an additional 4 hours of battery life to your MacBook Air and up to an additional 3 hours to MacBook Pro. The ChugPlug is compatible with all 45W and 60W MacBook’s, all MacBook Air and 13” MacBook Pro’s.

Available for purchase on Amazon.com for $79 and you can read more on Lenmar.