http://www.drillspot.com/pimages/269/26977_300.jpg
Cut off the corners
diagonally, making inverted ramps, to attach to the underbody of the car in front of each wheel. The same application behind each wheel would act as a fairing.
Each of these $5.37 polyethylene trash cans would make two deflectors.
Tough and resilient, these would resume their shape after hitting a curb.