Buy this but you may want to buy it from eBay or militant sleep system

It's not cheap, but this is what we used to get issued. The black bag might be what you want, I've used the green bag down to about 20 degrees and was still warm

https://www.amazon.com/Military-Modular-Sleep-System-Goretex/dp/B002LLPILC/ref=sr_1_2?crid=26VC93FEF0NZI&dchild=1&keywords=marine+corps+sleeping+system&qid=1605852541&sprefix=Marine+corps+sleeping%2Caps%2C226&sr=8-2