I have almost the same issue as my wife doesn't know about it (yet)...
I would suggest a lockable suitcase or chest. The suitcase can be placed in a closet. That way, if people open the closet by chance, they still haven't opened the suitcase (at least if they are well-mannered LOL).
I would also consider your car's trunk. But that's a bit more annoying as you might need the space when you go shopping !!!
