The Next to Skin Zero Wind jacket is everything you've been asking for - lightweight, breathable, waterproof and pack-able. They feature sealed seams and an lockable zip.
The jacket features a generous cut and a wicking fabric for soft touch around the neck. The elastic around the hips is soft and not too tight. They have a built in pocket with reversible zip for packing away in the back pocket.
Fully waterproof and windproof
Super lightweight and very breathable
Folds up to fist size
Relaxed elastic around hem and cuffs
Lining around collar for sweat wicking and comfort