As Hertz Gold or National Emerald Aisle, any SUV's you find on the aisles will most likely be something smaller than you're looking for such as a Rogue or Escape. Minivans are easier to come by so long as you're not traveling during a high season for family travel. "Lucking" into something like a Suburban or Expedition is highly unlikely. If you absolutely need something Explorer/Pathfinder size or larger, your best bet is to stick with an L4 reservation.