I put this usb adaptor under the seat and ran a cable up from there to my phone holder on my handle bar. Seems nicer than using the location on the dash. You could order ones with 12v plugs or even combo 12v/usb and fit it under there. I got the adaptor for the rear plug from eastern beaver.
I just wired an SAE connector from the battery up along the frame so that it comes out under the seat. I zip-tied the excess wire, and put a small bit of velcro on the connector and on the frame just under the seat. Now I can hook up my heated jacket with an adaptor for SAE to Co-axial, plus I can use the SAE plug to hook up the charger while in the garage. It was pretty simple.
I installed a Fuzeblock FZ1 under the front seat and added a 12 mm /DIN size 12 V output beside the seat lock. The place is tight for 12 V output, but it just fits when you move the wire harness during drilling/fastening.
FZ1 is handy, by just moving the fuse you can choose for every output if you want constant or switched power. FZ1 also includes a relay, so its super easy to install and provides 12 V power for up to six gadgets. The only con is, that max output is limited to max 10 A per output, 30 A totally.