"Most brewshops sell ""false bottoms"". Typically, it is a stainless steel plate with many small holes in it that allows your wort to pass through while causing your grain to form a grain bed. In the brewing industry they recirculate the mash (vorlauf-taking the liquid from the bottom of the vessel back to the top to further filter (via the grain bed)) in order to better clarify the wort before moving it to a kettle, or in this case to your fermenter.

I know for a fact most online brew shops sell false bottoms for both Igloo (round) coolers and 15.5 gallon kegs. I use a sanitary pump to move my wort, after vorlaufing, from the bottom of the mash to my fermenter...hope this helps."