GearBest.com has EasyAcc 11WL4U4A Travel Power Adapter with 20W US Plug on sale for $5.61.
Shipping is free.
● With a maximum compatibility of almost all smart devices
● 4 smart USB output, offer power to four devices simultaneously and avoid damage by providing smart charging
● Max 4A output, fast charging
● Folding plug saves space and reduces friction
● Power: 20W