I was thinking a low-profile tool box with socket rails riveted to the bottom would make a pretty nice portable kit.
This is the tool box style I had in mind:
I swear I saw one of those at Walmart for ~$7 recently.
Then just rivet a few of these to the bottom:
You can get these for cheap too. Like several for $5 cheap. Because the sockets would be vertical, you could fit a lot - and still have room for ratchets and extensions.
If it's just a 1/4" set, the toolboxes above are probably way bigger than necessary. I'd have to do some googling to see if there was an even smaller option. Cash box maybe?