I didn't want to lose my DS stylus when I travel this summer, so this was a good solution!
I changed the clasp to just a loop, for the DS lite.
I used Soft Flex (.014 in) for my string.
Make sure your leash is long enough for your stylus to reach the screen! I had to check a few times. The final length was about 6 1/2 inches with the (1 in.) loop on the end.
I priced it as "almost nothing" because I already had all of the supplies.