Opteka LP-E8 2000mAh Ultra High Capacity Li-ion Battery Pack for Canon Digital Rebel T2i Digital SLR Camera by Opteka (4) Date first available at Amazon.com: May 12, 2010 Buy new: $49.00 $12.95 (Ranking is updated hourly. Visit the Hot New Releases in Accessories list for authoritative information on this product’s current rank.)

Read more from the original source: 
#5: Opteka LP-E8 2000mAh Ultra High Capacity Li-ion Battery Pack for Canon Digital Rebel T2i Digital SLR Camera