Lepow® POKI Ultra Slim 5000mAh is fantastic as a short road trip battery. It's bigger than I want to carry when flying but is perfect for charging. Right now Lepow has their Lepow® POKI Ultra Slim 5000mAh External Battery Pack (Power Bank, Portable Charger, Charging Station) with 2.1A Output, Safe Lithium-polymer Battery, Fast Charge, Innovative Design and Compatible with Apple Iphone 6 Plus, 6, 5s, 5c, 5, 4s, Ipad, Air, Mini, Samsung Galaxy S5, S4, S3, Note, Nexus, Lg, HTC and Other USB Charged Devices (Apple Adapters - 30 Pin and Lightning, Not Included) -Lemon Yellow for cheap price. You'll just need to visit the site.
Why did Lepow choose this kind of design? With this slightly elongated design that gets thinner at the bottom of the product, it can be easily slipped into a backpack or purse. The slightly rounded surface and sides gives it more of an ergonomic grip as well for comfort and ease. (include what kind of material it is)