Andy
Somewhere on the car - under the hood, on a door jam, on the vehicle ID plate - there should be a paint code or number, which you can take to the auto parts store and ask for Pearl White metallic paint for that specific make and model car. If you just want a pleasing Pearl White metallic paint, not for any specific vehicle, then most large hardware stores and auto parts stores should sell it. You may need to be over 18 and show ID to buy spray cans of paint.
g
From any number of automotive paint retailers.
http://www.urekem-paints.com/pearl-car-paint-colors