I've had the best luck with the Igloo MAX 5 day coolers. It claims to keep ice for 5 days.
The key isn't really the cooler. Here's some unsolicited advise. First, use ice from your own freezer if possible (reusable ice packs work well too). Most purchased ice & ice machines like the ones at the Fort and hotels aren't kept very cold and the ice will melt fast regardless of the type of cooler. Second, chill the items you want cold before you put them in the cooler. Putting ice on warm cans & bottles will make the ice melt very fast. Third, drain the water out as the ice melts. Ice floating in water will melt faster. And last but not least, keep it out of the sun as much as possible.