Sure. I can fully recommend Porch Electric on eBay.
http://www.ebay.com/itm/Cub-Cadet-80...item41710f8ca5
I figured by the time I sourced all the proper connectors, terminals, different gauge wires and the outer covering...I could easily make more than the $80 or so by just going into work a little early.
Not sure about the heavy wire, doesn't appear so from the eBay pic. As far as the headlight "harness" there's really not much to it. Ask the seller, but I didn't even see one listed. That part may be where you can DIY.