https://www.harborfreight.com/2800-weatherproof-protective-case-medium-black-63926.html
The foam is made up of small square columns, I believe it's two sheets thick. So you can pluck just the ones you need to fit everything.
Water and fall resistance isn't cheap. There's lots of soft cases out there, but I wouldn't recommend any of them that offer space for the dock. they're basically flimsy versions of this case, with none of the customizability.
If you could live without the dock being carried around, that opens up a bunch of other options.
https://www.amazon.com/Carrying-Compatible-Nintendo-Portable-Protective/dp/B09YV65PTQ/