Could be custom. Is there an upholstery shop near you? If so, take the picture and see if they can make it for you.

Yes that's a good idea. I'll see what I can find. Thank you!

Start with the ones who do commercial seating such as restaurant booths. That's basically what those beds are with a mattress stuck in them.

Try looking at scandinavian design rather than Japanese.

https://scan-design.com/beds/