Welcome, I can tell you what I did for this.
I have a golden retriever that I take to work most days. But I also need to use the 3rd row at least once or twice per week. So I wanted a barrier that would go in and out easily.
I tried a "made to be a pet barrier" fabric type device (so it would store in the Armada) but that didn't work at all , she could push right past it. I looked at a friends "jail cell bar" type of barrier but that looked like a pain to take in and out and store in the back when it was down.
So after some experimentation, the cheapest and easiest solution I found was to just put a carabiner on the end of leash and clip that to the tie down at the back of the cargo area, near the lift gate. The leash is around 5' long and allows her to poke her head over the 2nd row so the kids can pet her, but not jump over. And she can walk all around the cargo area and not get tangled up. Now she just jumps in, and clip her in, and off we go. If she jumps out before I un-clip her she can reach the ground no problem. Plus a carabiner on a dog leash is awesome for tying them to something quickly.
To protect the carpet/fabric on the back of the 2nd row seat I bought some cheap vinyl from the fabric store, used a hole punch to poke holes in it so it can hang from the two outside 2nd row headrests, and ran the vinyl under the Weathertec mat back there. That keeps her hair off the seat and makes it easy to clean up - but i am a neat freak.