Sharkk via Amazon offers Prime members the Sharkk Aluminum Bluetooth Wireless Keyboard Case for iPad Air for $32.99 with free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, shipping adds $8.77.) That's $37 off and the lowest total price we could find, although we saw a similar case for $18 less last month. It features a built-in battery and includes a USB cable.