Join Date: Nov 2001
Location: Here, , Canada.
I'm not sure if Marmot still makes them but my Marmot Driclime sleeping bag insert is the bomb. It's lwt and compresses into a bag the size and shape of a 1L nalgene. I often use it on it's own in the summer or as a liner in the winter.
Another option is the Integral Design's Primaliner . I also on it...great as a stand alone in the summer or a liner in the winter.