Yubi Power YPOR61AB 30W 4-Port USB Rapid Wall Charger Travel Power Adapter for $8.99. Shipping is free on orders over $35. If needed, use this Filler Tool to pad the order for free shipping. Here is a screenshot for your reference. It has a compact unibody design for use on the go, along with foldable prongs for maximum portability. Most places have it for about $19.