That's more or less what I've found in other threads on the topic and what I was afraid of.
I'm probably going to have to think a little more out of the box.
I found these armless sofas
(and a ton of similar ones) on Wayfair that look like they'll fit in the space allowed. They look cushy and as a bonus unfold into a sort of bed if I dropped the table.
There are some other more generic sofas and loveseats that I could probably rebuild to fit in the space too. I have some plumbing and electrical that sticks up underneath one of the benches for the slide and the water heater under the other bench that limits how much demo and construction I can do in the space so this will be a real challenge.
Edit: Floor sofa is apparently the thing I'm looking for. Sold mostly for kids rooms due to the size but they happen to be exactly the size of a dinette bench.