Costco has some down blankets for about $20. I got one, folded it over, and sewed across the bottom and about a foot up the side to make a foot pocket. I added a buckle to match my quilt strap and use it inside the quilt. It adds about 10F to the warmth and weighs nothing. I do wish the blankets were a bit longer but it does help when it gets cold.
I bought 2 and sewed them together and added snaps for a cheap summer packing quilt
