Attached is wiring diagram for that circuit for an 03 Matrix, but it should apply to your 07 Vibe
You didn't say why you wanted the diagram, whether for repair or for mod, but here's one obscure thing to know about if its not working. The inverter relay, along with three others, is located on top of a small junction block in the dash up over the glove compartment. Some people have had problems with one of the relays (usually the TAIL relay) becoming unseated. You should be able to reach up around and over that junction block and press the relays back in, if that's the problem. Here's a picture showing the relays in the top of that junction block, after it 's been unscrewed and moved
If you need to pull that junction block down, there are three screws holding that in place, two are easy, one is on top and a pain to access. After the three screws are out, have to push up on it to disengage a plastic bit that snaps into a hole in the round metal support bar.
Now, if you're looking at putting in a more powerful inverter, the existing circuit only has a 15A fuse, so you'd be better adding another relay, activated by the existing relay to switch a new and more robust power source