Best Buy offers the Mophie Juice Pack Air Charging Case for iPhone 4 in White, model no. 1146_JPAXP4, for $47.99 with free shipping. That's the lowest total price we could find by $21. Sales tax is added where applicable. This 1,500mAh battery pack provides up to 6 hours of talk time or up to 5 hours on the Internet. It features LED indicators of battery strength and more.

Orders placed by December 19 at 1 pm ET are guaranteed to arrive by Christmas.