2018 2.5i Premium CVT
A quick look at the diagram says that it would be a challenge to do this for the front (lighter) socket in an SF (pre-2003) model. The outlet goes directly to the ignition switch via a fuse (#4 in the fuse block down by the driver's feet) that's shared with quite a few other devices. So there's no nice handy relay that could be bypassed to keep it on, as there is with the rear socket. I think the easiest thing would just be to run a dedicated wire straight to the battery via an appropriate fuse.