I have one of these stackable coleman ones and should fit with no problems.
http://www.coleman.com/product/24-ca...0#.VWCHBE_Bx8E
$15 [ame="http://www.amazon.com/Coleman-25-Quart-Party-Stacker-Cooler/dp/B00363PSBE"]Coleman 25-Quart Party Stacker Cooler, Blue | Amazon.com: Outdoor Recreation[/ame]
I have seen them recently at Target or Walmart and should allow you to put some things on top of it.
I'll try to snap a pic of it in the car later today.