Do you need a new wiper blade or just a wiper blade insert? If it's just the insert, go here
http://worldimpex.com/item_detail.html?sku=178825 and order two @ $5.54 each.
To change the inserts, gently pull the end caps straight out from the ends of the wipe blade. On one end of the wiper blade is a little metal prong that holds the insert in place. Gently pry it up with a screwdriver enough to release the insert. Pull the insert out, measure and cut the new insert to length. put in the new insert, push the prong down and replace the caps...