My 4x5 fortunately came with pelican style aluminium case, which I tend to use quite a lot with a regular shoulder slung camera bag for lenses/film holders.
Last year I splashed out and bought a Lowepro Dryzone for coastal landscape work. Fits all LF gear including 2-3 lenses, filters, meter, holders (outside dryzone). It's absolutely invaluable. It has saved all my gear once, perfectly, when I once went literally swimming with it.