Something that might be handy:
https://www.amazon.com/Upland-Scout-Waterproof-Protection-Valuables/dp/B071ZQDPCJ
https://www.amazon.com/Upland-Scout-Waterproof-Protection-Valuables/dp/B071ZQDPCJ
I've had several sizes of dry bags (not specifically this brand) over the years, mainly for extended canoe trips. They are very nice to have! I haven't priced them in 10+ years but that seems like a good price. Personally, it is an item best bought when you can get your hands on them though unless going off of really good information. There is s big difference in quality and ruggedness from one to another brand/model.
For go bags and such, it's a good idea to put a contractor grade garbage bag in your pack or duffel before you fill it.