USB Condom: ~$10, available. Tends towards either a bare board with USB connectors or that board with plastic shrink tubing on it. (https://www.crowdsupply.com/xipiter/usbcondom) (http://www.usbcondoms.com/) (probably an earlier version but the same person: http://int3.cc/collections/frontpage/products/usbcondoms)
UmbrellaUSB: ~$12, available soon? More polished/finished looking than the USBCondom, got their information on voltages from the USBCondom folks (see comments in the Krebs article above). Working on fulfillment of their Kickstarter (funded July 3). (http://www.umbrellausb.com/)
ChargeDefense: ~$??, a "coming soon" page, a picture of a prototype, and maybe more in September. (http://www.chargedefense.com/)
LockedUSB: ~$20, available. More technical details available, more expensive and very blocky looking - expect it to block any adjacent ports. Technical information indicates that the single unit should work with both Apple and non-Apple devices (https://lockedusb.com/product/lockedusb-adapter-charger-fire...)
Practical Meter: ~$20, available. Protects ONLY when used with their optimized 3-in-1 charging cables otherwise passes data through. Provides a 5-bar indicator of current. (http://www.powerpractical.com/product/practical-meter) more details in their kickstarter (https://www.kickstarter.com/projects/david-toledo/the-practi...)
PortPilot: ~$60, not yet available. Much more expensive, MUCH more informative, switchable between data/no data. Includes a display showing possible and actual power draw, etc. Almost a development/diagnostic device. (https://hakshop.myshopify.com/products/portpilot)
At least 3 listed below via Amazon (2 in UK): PortaPow $7 (2 versions, www.amazon.com/gp/product/B00GC4AJOU, looks like a "beat you to market" device), and Pisen ~$1.70 (http://www.amazon.co.uk/dp/B00E8ALIYU and http://www.amazon.co.uk/dp/B00E8AJ41E).