Why not make your own out of 1.3 oz silnylon plus some silicone sealer (hardware store variety is fine, thinning helps) and a bit of cord. Stuff sacks are the easiest thing in the world to make, as long as you can sew a straight line. Buy some silnylon (cosmetic seconds are fine), get scraps from a friend, whatever.
I like the RayWay design, with the long fabric tube at the mouth that can be wound up and folded back down. These are as waterproof as you can get in a UL stuff sack.
I also use a 2 mil polyethylene pack liner, just to be safe!