I wonder if you could find a junked Honda Insight and get some underbody panels from it that you could modify to fit under the Metro.
Provided the body is in good shape, it's best possible application would be a conversion to electric. Battery room out the ***...
A 336V pack of Optima Yellowtops and a 107 horsepower Siemens motor/inverter setup would yield ~120 miles range at 65-70 mph(Or about 180 miles range at 55 mph), 0-60 mph in ~8 seconds, and top speed around 150 mph. Would cost roughly $20,000 to do.
But why go through all that effort and part with all that cash trying to get an Insight undertray, when for much cheaper you could make your own?