Sleeping Bag Bivys $48 shipped! If you like your current sleeping bag set up but lack the water and wind proofing of the current Modular Sleeping System that I sell, You may wish to purchase just the camo Bivy. They are made of gortex material. Several members have reported sleeping in snow and rain with excellent results. I have a small supply of these. The bivy’s are in excellent condition and may have never been used.