Amazon with AnkerDirect has the Anker Astro Mini 3000mAh Ultra-Compact Portable Lipstick-Sized External Battery Charger Power Bank Charger (Blue) for $16
with free shipping. Compact charger adds more than a full charge or 9 hours of additional talk time to most iPhones, includes USB charger, and has excellent Amazon reviews. Also available in Black, Pink, or White for $16
with free shipping on $35+.