Using a 2-inch (standard) ice cream scoop, place 10 scoops of sorbet (from a 1-pint container) on a small, parchment-lined baking sheet or large plate. Freeze until solid, about 1 hour. In a punch bowl, combine 3 cups ruby port, 3 cups gin, 1 tbsp. agave syrup and 1/2 tsp. angostura bitters. Just before serving, pour in 1 liter chilled club soda and float the sorbet scoops on top.