Most photographers use props when shooting portraits. Props are simply items used to enhance the personality of your subjects or to prop your subject upon. In some cases a family pet is used as the prop.
Where does one go to find the perfect prop? Well just about anywhere will do.
My favorite place to start is thrift stores and flea markets. There is no rule that says your equipment must be new and unused so why pay and arm and a leg for something when you can find the same item used, that will work just as well? I also like to look through old barns and buildings for things like old wooden boxes, pieces of wood and old equipment. Ebay has a wealth of items suitable for a prop.