dunlop racing in Tennessee has them I think? Where are you located?
Here is a link for current compounds. Your 6680 is a Med+, see below..
http://www.dunlopracing.com/fitment.pdf
The compound is the 4 digit code stamped on the (left?) side of the tire.
Fronts:
6614 - Soft
6704 - Medium
6680 - Medium +
2783 - Daytona
6178 - old soft
6167 - old medium
6342 - old medium +
Rears:
7614 - Soft
7704 - Medium
6680 - Medium +
2779 - Daytona
7503 - old soft
7483 - old medium
7167 - old medium +
7127 - old medium +