Back before Christmas 2014 I bought a nice quad charger with 2.4 amp outputs on one of the "Lightning Deals" on Amazon. I can't recall the brand, but it was a pretty nice unit. I promptly cut it apart, soldered a fuse tap to the board and permanently installed it on the cross bar under the steering wheel under the dash. I have it powered through the seat heater fuse, which I'll likely never use. Right now I'm only using it to run my engine monitor tablet, but I have plans to add a new USB port to the center console since the OEM USB port there doesn't charge my phone worth a crap.
Edit:
Here's the one I bought:
Aleratec Quad 4 Port USB 9.6a (2.4 amps x 4) Rapid Car Charger for iPhone, Smartphones, iPad and Tablets
No complaints here, even if it is made in China