I highly recommend the Chillzanne bowls by Pampered Chef. They work great as does their platter. Since you probably can't order/get them by thursday(can you borrow one from a PC junkie,LOL?) how about making a bowl of ice for your bowl of potato salad to sit in.
Choose a bowl that's larger than the one you will be serving the PS in. Take the bowl you are using for the PS and fill it with heavy items that can be frozen (I've used bags of frozen veggies and the small size freezer packs) Cover well. Add water to the larger bowl then drop the smaller,covered one into it. Set it into the freezer and keep an eye on it to make sure the smaller one stays centered and "down" into the water. It's actually a good idea for the smaller ones rim to stay above the water mark, it'll keep the water from the melting ice out of the PS. Keep it frozen until ready to use and then just place the PS bowl into the frozen one. Should keep for a few hours if out of the sun.