Look around on Craigslist. I had a small Craftsman box for about a year, and I quickly filled it. So I watched CL for about two weeks, and found a nice sized box for $150 about a mile from my house.
Its used, but it does the job. I have most of my tools in there, but still have the smaller one for my miscellaneous tools, and keep my large bolts, tabs, and suspension parts in there as well.