Call Apple and ask for a new set, the will charge you shipping and handling. Should be $14.99 or £9.99. If the operative is in a very good mood and you have AppleCare you might get them for free.
They still did this at the end of 2010, when I needed to get some replaced for my MacPro.
They won't be the same as the originals though, as it'll just be a burned disc they do in the office.