I can't imagine what you're expecting that a dry bag couldn't handle. But if it's that bad, be sure to attach whatever container you wind up with to a completely secure object, so it doesn't float away. So you'll need a container with suitable strong attachment points, locks, cables, etc. Are you wanting to use these items you wish to protect on a semi-regular basis, or are you planning on packing them away and leaving them packed up? That would have bearing on what type of container you choose - you need to consider ease of access if that's a requirement.

Something like this might work if your scenario is pack-and-forget:

https://www.sportsmansguide.com/product/...-used?a=1009668