Invisibility Talisman/Item

Make invisibility talisman item, that is, while you're doing any kind of robbery you won't neither get attacked by someone, nor can attack anyone. And raise the chances of getting the talismans/magic items, in the Game Guide it is said: "You can expect to receive an item once about every 50 robberies" I do much more than 50 robberies a day and never got a single one of those.