Amazon.com : Synergy Digital Camera Battery, Compatible with Canon EOS 40D Digital Camera Battery Lithium-Ion (1500 mAh) - Replacement for Canon BP-511 Battery : Electronics
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Amazon.com : DSTE Replacement for Pro BG-E2N Vertical Battery Grip + 2X BP-511 Battery Compatible Canon EOS 40D 20D 30D 50D SLR Digital Camera : Electronics
Synergy Digital Camera Battery, Works with Canon EOS 40D Digital Camera, (li-ion, 7.4V, 1500 mAh) Ultra Hi-Capacity, Compatible with Canon BP-511 Battery : Electronics - Amazon.com
MeiKe MK-40D/BG-E2N/BP-50D Battery Grip for Canon D40 D50 D20 D30 | MeiKe Store