For Mark II owners, Amazon
has Zeikos ZE-CBG5DII Multi-Power Battery Pack for $50
with free shipping. Thanks, Andy! Sold out. BuyDig.com
has the Zeikos Vertical Battery Grip for Canon EOS 5D Mark III for $50
with free shipping. Functions as both a high-capacity battery pack and a vertical grip. The Canon-branded grip goes for at least $275.