Camper shell owners, need help with wiring

I recently bought a used leer 100xr from a guy for my 2013 dcsb in the back of the shell Mt here is a fuse box wire harness that apparently they just started using in the last couple years. It looks like the brand is "tag" there are two plugs that go in the top that are labeled chmsl-1a dome-5a and the other is aux1-10a lock/unlock the first has the wiring for the dome lights going into it, and the second is empty. The lower part of the harness/fuse box is labeled chassis input. I do not have the plug that plugs into the bottom which I am assuming runs to the battery or ties into the wiring in the bed somehow to operate the dome lights. Does anyone know where I can find this plug or how many wires should come out of it, in what order and where they should plug into? My local leer dealer is refusing to help me. Also it has a third brake light but I cannot find any wires for it or how to wire it into my brake light. Also anyone who has a short bed with the thule racks that could measure the channels that mount to the Topper and run the length of the cap, I would greatly appreciate it so I could order the proper rails. Thanks guys