I have two traveling tool kits. A road kit, and a smaller flight kit. This is the road kit:
All the drawers are shadow foamed to make it easier to tell if I am missing a tool (say a socket fell in the mud, or a colleague doesn't return something).
I built it with a used Pelican case I found on Craigslist ($100), Some left over HDPE for the drawer slides, and some 18ga sheet metal for the drawers themselves. There is a space in the bottom if I need to transport some extra tooling or components.
It took way too long to build, but it's already proved its mettle when a stevedore let some toolboxes go rolling down a gangway in dry dock and mine survived while a bunch of other guys had to sift through a pile of broken toolboxes and scattered tools. I'm sure luck played a roll, but I'll be damned if I didn't feel awful smug at the time.
The flight kit usually weighs between 50 and 70lbs and is easy enough to throw on the roof rack if necessary. The Road kit (pictured) can weigh up to 135lbs and is a little cumbersome to load in and out of the truck without help. They both easily fit in the cargo space and live there when I'm not working.