S60 upper third brake light wires

[afeeee]

Hello,

I want to modify the 3rd brake light but would need to place a module for that.
In order to pace the module I have to cut the positive wire that goes to the third brake light.
Does anybody know where this wire can be found and easally accessible without having to remove the headliner or so?
Can't find any info on where the wire harnass can be found.