MOTOPOWER MP0609 3.1Amp Motorcycle USB Port SAE to USB Adapter Electronics. SAE quick connector for your existing SAE outlet. With special mounting design, it can be mounted to amost any surface with tape, zip ties or screws ( hardware not included).
Was a little bigger than I expected for a single USB, but the build quality is great, easy to mount. I have not tested it in the rain as yet for waterproofness, though the cap seems to be a nice fit.