Amazon and other sites sell one that is shaped like an L somewhat. Blow up bed portion goes straight across seat and then goes 90 degrees to the floor to help provide a prop and large sleeping area.
They have different sizes I think based upon small pickup or big pickup.
It worked great and I spent prob 30 nights on it off and on throughout a year. It didn’t last too long (semi cheap).
But was nice to blow up with pump they included and then deflate to still have functional space otherwise.