I bought some at Pep Boys. They sell an assortment for about $10. We have some in stock if you can't find anything locally.
http://www.motowheels.com/italian/myProducts.cfm?parentcategoryid=507%7CDucati%20OEM%20Parts&productID=3003&showDetail=1&categoryID=509|Ducati%20OEM%20Engine&vendoridtodisplay=0&filterFor=&collection=168%7CEuropean%20Motorcycle%20Parts
http://www.motowheels.com/italian/myProducts.cfm?parentcategoryid=507%7CDucati%20OEM%20Parts&productID=3003&showDetail=1&categoryID=509|Ducati%20OEM%20Engine&vendoridtodisplay=0&filterFor=&collection=168%7CEuropean%20Motorcycle%20Parts