$90 - Spindrift Sock - 2 doors - adds about 10 degrees in the cold and also provides rain/moisture protection
Used twice - I'm not a cold weather camper

$100 - Ridge Creek XL Underquilt - Blaze orange (out) and black (in) - 3 season (~25 degrees)
Used maybe a dozen times, motorcycle camper, stored in smoke free environment.

Price include shipping conus.