A pass-through harness would be a good way to do it, if you have the right crimper. If not, solder would be much more reliable.
If you look very, very closely (get out your magnifying glass), there will almost always be some manufacturer's mark on any modern automotive connector. My top-of-the-head guess would be that these are AMP Superseal plugs, but I could be wrong. In any case, once you identify the type, they'll be easy to find from places like Digikey.
Edit: just went out to my 2011 and I see "AMP" on at least one of the tailgate connectors.