Used a modern military Patrol Bag with Gore Tex cover I got off Ebay cheap .
Cut a cross shapped cutout in the bottoms and stiched around it to keep from fraying so I could slip it over the foot end of the hammock and pull it up for a foot box as well. Sewed on a couple of grosgrain tabs to use for mini bungee cords at both ends to keep it close to the hammock body.
I've been in the teens with it and slept nicely.