Tensun via Amazon offers its Tensun International Travel Plug Adapter with Dual USB Charging Ports in Black for $17.99. Coupon code "9P3G328L" cuts the price to $11.95. Plus, Prime members receive free shipping. That's $27 off list and the lowest price we could find. It features four built-in plug standards (US/EU/AU/UK), two USB charging ports, and a slide-out plug release button.