>>2257409 I have one like that, it's amazing. Used it summer to November this year on off-road trips down to 1°C.
I use a thin foam mat. My inflatable pad (klymit Insulated Hammock) and my down blanket and clothes as pillow case.
I got it one bay almost new for 40 Eurodollars with a patch kit because it had some scuff marks
so do check there, you can get plant from EU army surplus like this
https://www.ebay.de/itm/255229864271?hash=item3b6ce2a94f:g:t9EAAOSwNslhkqwf