All4Cellular offers the Stitchway 1900mAh Backup Battery for iPod / iPhone, model no. CHEX-ALL-BK-08-319, for $6.95. Coupon code "A4C2012" drops it to $6.12. With $2 for shipping, that's the lowest total total price we could find by $1, although we saw it for a buck less in March. It purports a full charge in less than two hours.