Another vote for gore-tex paclite. I bought super minimalist one for cycling, it's basically a shirt. It works great for "double bagging" under various gore-tex or e-vent shells. Never been wet under some hellacious conditions that eventually wetted out the outer shell. Stopped by the thrift store last week and scored an almost new marmot waterproof breathable shell that has a carhart-ish twill outer layer with elbow patches for $20. Should be more durable than ski type shells. They also had a giant can of 13% silicone kiwi camp dry spray for $1. Not sure if treating the outside will gum up the membrane, but for $21 it's a cheap experiment.