Sleep mat - anyone got one like this?

[unlikelychump]

I'm looking for a sleeping mat for a caravan. We currently have a mattress topper and a sheet which is very hard to tuck into a weirdly shaped bed.
What i would like is a large rectangular padded mat, which can double as a sheet. And then goes under the coverless duvet. So a padded coverless sheet if it exists.
Washable too.

Does this thing exist or do I need to invent it???

https://funnyfuzzy.co.uk/products/garden-chic-cotton-sofa-protection-cover?sku=18059110008482389513443061&utm_source=google&utm_medium=shopline-feed&gad=1&gclid=Cj0KCQjw2qKmBhCfARIsAFy8buLHbjrnZqzFRzVTgLVsI0HFQWMKj9OmtpN8dvw-kAhNDdRNAPnZKEsaAtimEALw_wcB

Funny as I was thinking about something similar- this is the closest to my vision but I think all the quilting would be a bit uncomfortable- along these lines though.

Yes! Something like this

I have had a brief foray into futon mattresses today, but they are big to store and covers not washable. So I have ditched that!

Rectangular mat, but with pillow case or duvet cover style cover. Slide mat into cover and fasten up. Stays with mat so no need to tuck in. Remove to wash?? Should be simple enough to make the cover out of cotton fabric.

Oooh this is exciting!