"Over the past few years I have had to make a lot of Minimate shoulder straps, pieces of armor, knee pads, and skirts. Usually a piece of thin plastic works much better for these than sculpting clay, because you don’t have to worry about sanding in tight places, and it is easy to get crisp straight edges."
This is a small sheet of 30mm PVC plastic which can be used for customizing. It measures 3.375 inches by 2.125 inches (the same size and thickness of a credit card). However one card can last through many customs depending on how much you need. See the photos above for an example of how it can be used with making custom minimates.
This plastic can be cut, glued, and folded. However the color will fade at the joints when folded. See the additional photos above for details.