For the pizza box, it is available on the store. Note cold pizza slice is different than the one you randomly get from missions, "Discarded Pizza", which you put on the pizza box if you have any.

Go to: cards > your collection > boosters.
From there you can purchase it, be sure to have enough balance on your hive wallet.

Leveling up will be easier once you have pizzas because it will lessen the energy problems.
!PIZZA