Here’s another item for the “enclosure ideas” area –
This portable USB charger was built using a Li-ion battery pack from a surplus Qualcomm phone and a pricey-but-efficient voltage step-down circuit. What seems most unusual is the enclosure chosen –

Now we’ve got a working product, but it’s still bare electronics. They’d never let me board a plane with it looking all suspicious and improvised like that. It’s got to look good, or at the very least innocuous. Enter this faux-leather material that I bought at a local fabric store. It’s expensive per yard but fortunately I didn’t need much of it!

Interesting choice, would probably look fairly “at home” on a key chain. Not sure the TSA would gloss over it so easily though, what with the unbound stitching and visible LED. –Link

In the Maker Store:
Minty Boost
Minty Boost battery powered USB charger –Link