I bought a metal briefcase type toolbox at Menards that has foam inside that can be cut/pulled out to fit your locator. I was able to put an LCX17 and a 107DF in it with the RAM mounts. I only paid about $20 for it.
I usually leave my locators on the boat, but when I do take them off I put the cover on the screens, put each one in a pillow case, and I have a cardboard box that they all fit into.
I figure they must be pretty durable considering the pounding they can take in the boat.