Improvements offers this LED Illuminated Buffet Cooler for $13.95. Coupon code "MM6W123" drops it to $3.95. With $7.95 for shipping, that's $26 off list and the lowest total price we could find. This inflatable cooler includes a freezer brick, measures 48" x 21", and requires three AA batteries (not included).

Update: The price has increased slightly to $4.97.