I dont know aboout store bought icing but if you wanted to make some you could with ingredients you most likely already have in your home....
margerine or butter
powdered sugar
vanila
you can make a lot or a little depending on how much you need .Put the butter or margerine in a dish pour enough powdered sugar to cover and add a couple drops of vanilla. If it is too wet add more sugar ...too dry add more butter etc.