The foam hand is found on the blimp that travels high in the sky around the map. It is denoted on the map with a red blimp shaped icon. The Booster Arena Club is located in the north section of Booster City. You can complete 50 deliveries with a gold rank to unlock the UFO, which is the best vehicle in the game.
Here is a video guide with English commentary!
Here is a playlist of guides for this game!
https://www.youtube.com/playlist?list=PL-HeW6XkKdUISTHMzTXDO...