B&H has the Polar Pro PowerPole for $44.99 (reg. $99.99) as its Deal Zone deal for the next three days. It provides continuous power to GoPro cameras. Read my PowerPole Review. Check out the deal here at B&H Photo.
Note: This is labeled as a white box item, which means it was likely taken from a Nikon DSLR kit to sell separately – hence the low price. At the time of this post, ebay seller GetItDigital has a 99.7% positive feedback rating.