They sell these at Michaels. They're doll cases.
Last year they had larger ones (to display wine bottles), but as previously stated, they were discontinued. The ones that are out now will work fine, the only problem is, depending on the height of the figure, I doubt you can have a display stand in there with them. My DX 13 fits in there perfectly without a base, but say a taller figure? Probably not.
They're on sale a lot, 50% or BOGO free. You're looking at about $6-$7 a case. It has a porcelain looking doll on the inside (that tears off).