I don't think these are sold in the US yet but an option for those who want to keep the second row.
"The Ququq Flatbox weighs 139 lb and is designed to be installed and removed so the Land Cruiser can be used for camping and for everyday use"
Flatbox kit turns the Toyota Land Cruiser into an overland camper
Ququq already offers affordable all-in-one camper solutions for some of the world's most rugged off-roaders, with its Land Rover Defender box and Mercedes G-Class box. Now it's adding something for what might just be the world's most universally beloved overlanding machine: the Toyota Land Cruiser.…
newatlas.com
"The Ququq Flatbox weighs 139 lb and is designed to be installed and removed so the Land Cruiser can be used for camping and for everyday use"