Just search on "Monoject 412" in medical supply houses.
Online dental supply places have these for about $0.55 each qty 50.
Try this [link=http://www.henryschein.com/SrchResult.asp?SearchType=1&keyword=monoject+412&s 8fid=24011230646164]link[/link]. (I have not purchased from this supplier)

I just ask for a couple when I go to the dentist.