I don't know how giant they are, but coastalscents.com has some that look exactly like Sephoras but they are like $20 instead of $100. Also, maybe you could check places like Home Depot? Some of their tool organization things might be useful.
I'd say to go with an actual tool box like the kind they sell at Home Depot or Lowe's. I can't remember which poster it was, but someone has a picture of one being used as a traincase/storage area in Stash, Stats and Storage.
Alternatively, have you thought about getting one of those small plastic drawer stands they sell at places like Target? I use that for mine once I realized they just don't make traincases for collections like mine.