These are commonly called
They come in different sizes, make sure you buy the size for your fuse box.
Tap a fuse always hot or ignition controlled, your Choice, and run a new wire from the fuse block.
It will be longer than you wanted by tapping the lights but it'll on its own fpiggy back fuse and supply uninterrupted full power.
Post 119 in my signature thread (below) shows some USB outlets I've added.
I've also added these in the bedroom and I think the bathroom.
(there's installation info in my thread but I don't know the post #.)
I can't think of a way tapping before the switch can activate the lights unless they loop feed like a ring counter. I don't think loop feed ring counters have been used since the 8008 days.