you can put it in a tub with cold water and put a tshirt of the carboy. As the water wicks up the shirt it will evaporate and help cool it down. You can also put some frozen bottles of water in there with it that will help too.
I found the juice at the store again and added it to secondary. It tastes just as good as cutting up a melon and juicing it yourself and its a lot easier. I will keep using it as ling as I can find it.