DIY - Mobile USB Charger : 5 Steps (with Pictures) - Instructables
Amazon.co.jp: External Battery Pack Shell, L12 10W DIY Portable Power Bank Case, Battery Charger Outer Case with LCD Display, Micro USB + Type-C Input, 2 USB Output (Black) : Electronics
DIY - Car Charger - Team-BHP
DIY Dynamo USB Charger for a Bicycle | 自作の自転車用のダイナモ充電器(USB… | Flickr