Hoods' Woods Mini Kit Sparkers (1/8 by 2 inch Ferrocerium rods, each in its own ziplock plastic bag - no magnesium block or striker included)

Go to
http://www.survival.com/products.htm

click on the Online Store and the on the left hand side, click on "Product List", go to the bottom of the page.

$3.50 each, or 5 for $15. (I bought 3 packs of 5, in a fit of exuberance; each one came in its own high quality mini-ziplock bag, which can obviously be re-used for other purposes.)