The Hoverboard can be acquired via giving all four Trophemon to a single group: The Eccentric Millionaire or The Activists. The Activists can be found during the evening, in the courtyard to the right of your basement house. The Eccentric Billionare can be found up the road between the Mobster Tower and the Cozy Condo at night. If the player does not give ALL four to one group, aquiring the Hoverboard will be impossible. Giving the Trophemon to the Activists will give you positive Karma (and the Hoverboard), while giving them to the Billionare gets you $1000 per Trophemon, negative Karma, and the hoverboard.