AirBedz Lite (PPI PV203C) Mid-Size 6'-6.5' Short Truck Bed Air Mattress (72" x 55" x 12" Inflated) https://www.amazon.com/dp/B00O4Z5XOA/ref=cm_sw_r_cp_api_glt_fabc_VJ34KSAG9SVW6YR2FXWF?_encoding=UTF8&psc=1
I’ve got this one and it fits perfect in my 5th gen. Very comfortable even with 2 people
Here is the link for the air mattress
https://www.amazon.com/AirBedz-PPI-PV203C-Mid-Size-Mattress/dp/B00O4Z5XOA
It is great sleeping in the back of these. It's made camping so much more enjoyable and easy.
I'm using this air mattress that I was using in my frontier before I got an xterra. This is a thicker mattress and goes over the wheel wells. It fits perfectly in an Xterra too -
https://www.amazon.com/gp/product/B00O4Z5XOA/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
If you haven't already bought or made them I suggest making insect screens for your window and hatch. They can be made economically and rugged, or expensive and nice looking. We chose economical and rugged, in case we made any mistakes. The way we created them was by buying insect window screen from Amazon and cutting it to size by placing it over the windows and hatch. After, we bought weather proof gorilla glue to glue simple mass-produced circle magnets onto the screen around the edges of the cut screen. Overall, it was incredibly easy to make and doesn't require any extra skills besides cutting and glueing. Some folks that want to spend more or have the skill sew sleeves around the edges to hold the magnets instead of glueing it ( https://theskeeterbeater.com/ ).