That's it!
http://www.campmor.com/outdoor/gear/Product___77708$39 dollars, weighs 16 ounces, fits in a stuffsack the size
of a pint water bottle,
taped seams, good for raincoat and pants, and for unexpected
bivouacs it beats a garbage bag.
The military bivy bag probably weighs more than twice as
much, costs more than twice as much, and then you need to
buy a rain coat and pants too.
All trade offs.
If I plan to sleep out, I will bring more
stuff for comfort, maybe a bivysack if the weather calls for it,
but if I am just out for the day, I am not going to lug a whole set of overnight gear.
For one night out, impermeable bivysacks,
or just rolling up in a tarp work okay anyway in my experience.