I’ve been meaning to get a roll-up tonneau truck bed cover for that very reason. I have a crew cab, so a decent amount of cargo space in the back seat, but my dog is always back there these days, so I need a solution myself. I want the roll-up kind though so that I can still use it as a truck on a whim when I need to. That would work for you too. Then cut a couple 2x4s to the right length and put them in the slots around 2 feet back from the tailgate to create a wall for stuff that can’t slide around.
I’ve been meaning to get a roll-up tonneau truck bed cover for that very reason. I have a crew cab, so a decent amount of cargo space in the back seat, but my dog is always back there these days, so I need a solution myself. I want the roll-up kind though so that I can still use it as a truck on a whim when I need to. That would work for you too. Then cut a couple 2x4s to the right length and put them in the slots around 2 feet back from the tailgate to create a wall for stuff that can’t slide around.