Ditto the quilt, and ditto checking for an EN rating.

A high quality down quilt will be less expensive, lighter, and more compact than a bag. The one I got, made by enLightened Equipment, is long enough to be pulled over my head as a hood and has snaps and draw strings to hold it together if needed. It's not as convenient as a zipped bag, but every design is a compromise. If you figure you can live without a zipper, there are savings there. The quilt is a favorite addition to my three-season bike touring kit.