Here is what you need:
1.) One Sugru pack (you choose your favorite color)
2.) One potentiometer without "head" that is annoying you
Procedure is really simple and can be understood from photos. You need to open Sugru, make a shape that fits to your potentiometer's top and after that place it around and press a bit with your fingers so it can stick really hard to potentiometer's top. After that leave Sugru to solidify and your job is done.
Good luck and have fun :D