That's vynel tape or as we call it "contractor's tape." I always ask for a roll or two when I am at an abatement project and keep a steady stash. Apparently it is $8 wholesale and like 12 retail per roll. Comes in 2, 4, and I think even 6" wide. They order it by the pallet.
Walls went in. After a test fit a layer of Refletix was spray glued to the back of the panels. Suddenly it is very hot and quiet inside the van. I had to work with the side doors open.
And I blocked off where the bed would be. I'm going for a fixed C with back rest cushions that fill in the bed. I haven't seen it done before, but I seems like a good hybrid. I haul around a ton of gear in my truck, but I also need to be able to seat 5 or so for shuttling around the river.