You don't have to buy one either. A suspended wet towel with a fan blowing on it will work very well. If you want to get fancy, have the last inch or two of the towel sitting in a tray of water.
My brother's house in Perth, Australia has an antique air conditioning system in the roof space that works in exactly this principle. 4 blankets that wick up water and have air drawn through them and into the house by a fan. It's in disuse now but I understand they were common and quite effective in the day.
You don't have to buy one either. A suspended wet towel with a fan blowing on it will work very well. If you want to get fancy, have the last inch or two of the towel sitting in a tray of water.