Got this mood done the other day, works well. All done under the hood, completely reversible, not cutting required.
Get a micro sized tap a fuse, a 12v relay, some male/female spade connectors and a bit of wire.
In mine, there were 2 unused fuse sockets that were keyed with the ignition. I installed the tap a fuse and weird it to the relay to drive the relay. I pulled the fuse for the front accessory port, and wired it online with the switch side of the relay. The spade connectors fit the fuse terminals perfectly.
It's not perfect, the circuit I used is only powered in the "run" position, not accessory. But it was better than always on.