Can be made from a crafting catalyst from crafting dragon hides, soft leather, hard leather, imphide, spider silk, carapace, bat wing, snake skin or yak hide (one leather case per item and per catalyst).
Extra parts of gem foci, metal settings, and leather cases can swapped at the Crafting Master in the Crafting Guild, even if one does not meet the Crafting requirement to enter (knock at the door).