This activity is best done onto a paper plate that has been divided into a fraction appropriate for the student. If a paper plate is not available a round piece of coloured paper will work the same and can also be folded into a fraction easily.
Each of the toppings can be printed onto an appropriate piece of coloured paper for students to cut out and stick onto their pizza. They then write the fraction that topping occupies of their pizza.
At the end of this document there is a rough example although done on the computer as I forgot to take a photo of the students work.