I had this sleep sack, and it was super versatile and easy to use. In fact I had several of them and wore them all out in my touring kit years ago--so lightweight.

For more intense, long-term, I recommend this one (I know it's a UK link, but y'all can figure it out.) It's thicker--more bondage-y experience--but breathable for the skin, and, best of all, machine washable after containing hours of that sweaty bondage monkey in there.