I am thinking it will depend on if you want the light on at all times or only when the rest of the interior lights come on, as in when you open a door.
If you want it on only when you open a door then tap into the wire that runs to the passenger door for the lighting. If I remember correctly, but don't take my word for it, the doors are wired together where the passenger door is wired to the driver door.
If you want the light on when the headlights come on, as do a number of the small interior lights, then you can also run them off the passenger door wire as there is one for the door handle light. You just need to test to find the correct wire and then tap into it. All the door wires, from both sides, run as a bundle from the door to compartment up behind the dash. It may be a PITA to get to it all but I am sure you can if you take your time.
As for actually doing a custom plaque that allows for a led to be behind it I would say <removed>