Look for any 2-amp (2A) usb wall wart, and a usb Micro (not Mini; plug shaped like a hat) to USB-A cord that plugs into the usb socket on the wall wart. These can be bought cheap, often $10 or less.
Also, any cheap USB power bank, as long as it rates to 2 amps, should do. Also, if you haven't yet, get the large internal battery, and battery cover that fits it, if you haven't already! That usually gives you at least 6 hours continuous use on a single charge, plus if you get the external battery charger, it comes with a spare large battery. Worth it, too, though it'll set you back about $60-$70....