Outdoor rated tool chest?

I was wonsering if any members knew of a roughly 11-15 drawer tool chest that has an outdoor rating? For my work I need to ship my tools from jobsite to jobsite and often times they need to be left outside for days on end in minnesota weather. Currently we use knaack boxes with 4 drawers that work well but im interested in something that I can organize my tools a little better. Looking for a chest that is lockable and on casters. It will be used in an industrial setting so I would like a chest that is well built. Any ideas would be appreciated