It isn't hard, get all the old flocking off and replace it. A good hobby shop should have flocking material, if not the local high school wood shop teacher will probably know where to buy it (think jewelry box projects etc). The old flocking usually comes off very easily with light scraping. Spray or paint adhesive on the plastic and then your choice of flocking color liberally heaped on and spread around. Let it dry and then shake the excess flocking back into the container.
PS, you can practice on any bubble package, egg containers, or even the back of the presentation box insert.