Bilboberry
The Hobbits' favorite medicinal berry.
Medicine made from the Bilboberry will exist and treat you effectively as long as you're inside the bright 'n' balmy lands of The Shire, but just like Dorothy's silver shoes and magic belt that will vanish once you leave the Land of Oz, said wondrous elixirs will disappear from your pockets or saddlebags if you head out into the Big Wide World of Middle Earth.