Last year, Joann's (the store, not sure about online) had some really cute and inexpensive tins that they had on sale sometimes, othertimes I used my coupon, and they came in a variety of sizes, shapes and they ranged in price from $1 to $5 after using the coupon.
I know some of them would have fit cards nicely. ;)
Do you have a Dollar Tree or a store similar near you? They sometimes have tins too.
Also, maybe getting a paper mache box and covering it with pretty papers &/or stamps to coordinate with the cards?
Good luck, I hope I helped you a bit!