Amazon has Apple Smart Battery Case (for iPhone 7) – Black on sale for $49.99
Shipping is free w/Prime
The Smart Battery Case for iPhone 7 gives you extra battery life with the look and protection of an Apple-designed case.
Combined with the Smart Battery Case, iPhone 7 provides up to 22 hours of battery life for browsing the web, up to 24 hours of watching HD video, and 26 hours of talk time.
The Smart Battery Case also works intelligently with your iPhone to charge simultaneously when you’re plugged in, so both case and iPhone will have more than enough battery life to get you through the day, and then some.
The soft elastomer hinge and one-piece design make it easy to put the case on and take it off. You can even connect it to any Lightning accessory, such as the Lightning Dock.