We used a silicone coated nylon, but any other light or medium weight fabric can be used. In general, silicone coated fabrics are very slippery to work with and a teflon coated sewing foot is essantial for the sewing machine. A thread with cotton/polyester mix will expand when wet and helps sealing the seam. For more waterproofness, seal the seams with a silicone glue.
The chaps are easy to pull on over the shoes and fixed with one strap to your belt. The open hem version is very easy to pull over your shoes. The elastic and gaiter hook version gives you more usability, as it lets you cross water ways and your feet stay dry.
The grip elastic and gaiter hook adds a nice feature.
In the Image below you see how small the whole rain gear set packs is. The chaps fit in a men's hand or pocket. And the whole set includes a long coat and over mittens.
Eta-Proof Outdoor Pants