You are provided a case by PrepLounge that you can use.
That said, I would recommend against the approach of randomly learning a case 1 minute before you have to give it to somewone!
Rather, you should fully learn a case beforehand and give the individual that case. Better yet, case them in a case you already did and struggled in! This way you can see their approach, what they do well and what they don't...make is so that you're not just "giving" a case but actually learning from it!