I lost the nose pad on my beloved Oakley Sunglasses.  In order to buy a replacement, I had to get a whole kit from Oakley which was going to be $10 plus shipping.  Instead I created a design and printed out a replacement.  The first replacement lasted about 6 months, then after the glasses dropped once on the floor, it cracked.  I printed out a few extras this time.   The replacements just snap in place.