This is one way to do it:
Add an instance variable to the items you will use as price.
Each item has a different Integer value starting at zero (e.g. t-shirt=0, baseball cap=1, shoes=2, etc.)
When the player inserts the token to play lottery use floor(random(n)) where n is the largest index
do a for each loop for the prize item and pick the item whose instance variable matches the one chosen by floor(random(n)).