Here is a great stocking stuffer for you! Amazon has this INSTEN for Apple® iPhone® 4/4S Sport Workout Armband – Black/Sliver for just $2.54 with FREE shipping! (reg $9.99)
There are other you can choose from for cheap as well!!
Sports Armband Case for Apple iPhone 3G/3GS and 4 - $5.41 + $0.50 shipping