So one morning my fifteen month old son was playing and I was chatting with his mother when he reached up onto my shelf and pulled down Batman: The Animated Series Volume III and ripped the box clean in two. Now as a man who loves his box art, especially his Batman related box art and may be a tad OCD about things I nearly had a nervous breakdown. Yes, my son is still walking, breathing and breaking everything under the sun but I'm fairly well inconsolable in that charming man-child way that I possess in spades. The DVDs themselves are fine, the inner sleeve is also in great condition. The only issue is with the outer box. I don't want to spend 30 bucks to get another box. Are there any sites out there that just sell the cardboard outer boxes? I'd be willing to spend a few dollars to replace the box art. Anyone have any ideas that don't involve me buying the set again? Shoplifting doesn't count.
Maybe try e-mailing WB (it's them who did the DVDs for Batman, right?) and see if they have any options for you? Kinda like when you get a faulty disc they send one back to you. Maybe they have something they can, even for a price you find reasonable, send your way? I dunno. Just a suggestion, otherwise, I pretty much have nothing.
I'd be very surprised if they manufactured significantly more boxes than DVDs - they are meant to be sold as a set and the market for replacement boxes would probably be too slim to bother with. You might find a second hand copy of the set going cheap on Amazon marketplace or eBay - it wouldn't matter if the discs were in a poor state if it was the box you were interested in.
There are also websites where fan-made box-art is up for download, to be printed out and then used as sleeves for generic DVD cases. You might be able to find something looking those up. You'd need to get empty DVD cases and make print-outs for all four volumes to have a matched set, but it'd still be cheaper than rebuying the DVDs, in all likelihood. Or if you do get a new one, you can just ebay the discs (and taped-together box) for someone less fastidious than you to buy, make back a few bucks.