I just picked up a load of USGI intermediate cold weather sleeping bags in very good condition. These are the black bag that is a component of the modular sleep system.
Adjustable hood
90 inches long x 36 inches wide
Solid black
It's rated down to -10 F. Realistically most people will be comfortable into the low 20's.
I'll post pictures when I can, but you can google images.
$30 plus shipping.