I have (more than) a few of these. They are new take outs from Ford F series trucks from approximately 2015-2020, but if you were so inclined, I'm sure you could stuff them into other trucks/boats/airplanes/projects/static art. They are the Swiss Army Knives of the Seating Universe because they fold, unfold, open up in different ways, and ummm, store things. They come with seatbelts and plenty of storage to stash your stuff. Or stuff your stash. Whatever. They have been sitting around, so some are nicer than others. Prices range from $80 for the nicest ones on down to $45 for ones that were caught in rainstorm while loading.
They measure 23" long by 15" wide at the base. (The widest part)
Did I mention they have cupholders? Soooo many cupholders...
The more you buy, the cheaper they get. (I'm already really cheap, but I ain't easy) Located just SW of Chicago in Historic Oak Lawn, the Crown Jewel of Chicagoland.