Maybe Ianto should replace all their buttons with velcro - it makes for much easier access ;)

I can so picture Ianto with his jar of identical buttons. adding all the ones taken of Jack's ruined shirts just to keep in topped up.

I can also imagine Jack going through Ianto's wardrobe, removing the bottom button from each shirt, and presenting them to Ianto saying, "There, now you have a spare button for all your shirts."