Re: bivvy sack

I have (or had - not sure where it is) a Gerry sleeping bag cover - it was an uncoated nylon bag with a half length zipper and a drawstring at the top - it was not a bivy sack per-se - but rather just a cover for your sleeping bag.

I doubt that they've been made for 35 years - mine is the only one I can recall seeing - but it did serve well on the Appalachian trail in summer time (kept the bugs off and provided some level of modesty in trail shelters) - it would have been really nice with a light fleece bag inside it ...

If you're looking for either an uncoated one or fully coated one I cannot imagine an easier sewing project - then you could control the size, the material, the zipper location (if any) - mosquito netting (again, if any) -