I'm using VHS tape boxes for it (new old stock, got a big package of it from eBay), padded with self adhesive foam inside, so that it doesn't rattle. There are different versions of it, I have one where you can insert a cover, which I will let print professionally later. But looks already surprisingly good with my color laser printer.
Edit: I have 85, I guess I won't need all, can sell you the rest in 22 days after the Kickstarter campaign.