What is the current draw on your other device? If you're just charging a BBU for the dashcam, it's likely 3A at most?
FWIW, I used the console USB to get ignition power to the rear for my TPMS transmitter (USB input) and just plugged in a 90° adapter and ran it in through the cubby, down, and under the carpet.
I think Jimmy said the mirror (on a 10A fuse) is around 1A? the USB would likely draw less than 3A.
I believe these are the fuses that are in play:
F80 | / | ATR (Micro2) | 10 Amp Red | Universal Garage Door Opener / Compass / Anti-Intrusion Module (DS 1500 Only) ASSY Overhead Console / SW Assist / SW 911 – If Equipped (HD Only) |
F90/F91 | / | ATR (Micro2) | 20 Amp Yellow | IGN or BATT Customer Selectable – If Equipped (HD Only) Power Outlet (Rear Seats) Customer Selectable (DS 1500 Only) |
F104 | / | ATR (Micro2) | 20 Amp Yellow | Power Outlets (Instrument Panel / Center Console) / Trunk – If Equipped (DS 1500 Only) UCI Port / USB Rear (HD Only) |