Arts-and-crafts "super-stores" (like Michaels or A.C. Moore in the US) have nice, cheap unfinished wooden boxes and chests of various sizes, some with brass hinges and claps and some with removable lids, that work very well. I leave mine unfinished so the wood can breathe and wick off any condensation. I only have around a dozen decks, so I keep my favorites in wood and leave the rest in their original boxes on a bookshelf. If I'm entirely indifferent toward a deck, I might just throw a rubber band around it.