If you’re on a hardwood floor a simple tatami mat (or stiff foam faux tatami) will provide some insulation from a cold hardwood floor without making the sleep surface too soft. Something like this with a blanket on it.
My kids and I sleep on this , https://www.amazon.com/Leewadee-Mattress-79x41x2-Premium-Stitched/dp/B00QT1CUEI. With one blanket over it. I like it but def recommend finding a sheet to put over it. It can be easy to clean because the cotton inside is super dense. Just wipe off and dirt or spills. I also lay it outside to let the sun clean it. I do t suggest hosing it down as it could mold u less you have is tense sun like FL or AZ. It’s super easy to travel with
One of these bad boys