PC Micro Store offers the PureGear Rechargeable Battery Pack for Apple iPhone 4 / 4S in White, model no. 33121PUR-WH, for $19.99. Coupon code “33121BATTPK” cuts it to $9.99. With free shipping, that’s tied with our mention of a black one from four weeks ago as the lowest total price we could find, this time by $10. It includes a micro USB cable and is also compatible with iPhone 3 / 3GS. Coupon ends after 2,000 redemptions.