You can get USB ports integrated right into your outlets. Jody Victor‘s crew found an article that shows a lot of information about the correct way to wire one if you choose to do it yourself.
They suggest you get stick with UL-rated outlets not only for your safety but for the safety of your devices. They range in price from $20-$40. You can find them at The Home Depot or Lowe’s or probably most any hardware/electrical supply store.
Here is the article: http://www.howtogeek.com/244537/how-to-upgrade-your-outlets-for-usb-charging/