I'm auditioning two boxes right now. I found a box that I'd bought from the dollar store a few years ago that is the perfect size for the folders and dividers that I've been using. As you can see, the dividers are from the packaging. They already had the name on them, so why not?
The other box is a 4 x 6 file card box from Wal-Mart. It was only $1.49 and I think I like it better. I'll have to make dividers or at least trim down my current dividers to fit this box. I haven't made it over to Target. I still may go check out the accordian files that Monica suggested.