rcaoili - you can order it from an automotive paint store. But, it's about $100 for a 40 yard roll. Since you only need a 1" x 1" square (enough for about 4 1/2" x 1/2" squares) you're better off to find the dealer in your area who instals the clear bras, and ask him for a small scrap piece.
Try
http://www.xpel.com and look at their local installers to see if there's one near you that you can beg a scrap from.