There are quite a few epoxies that are very good at thermal conductivity while also being electrically isolated. Just not sure what your operating temperatures are at.
I would think you could apply the epoxy to your heatsink, let dry, then mount the star.
Frys more than likely carries such a compound or grease. I haven't personally looked in my hours of wandering the store looking for ways to waste money, but its probably worth a look
Another type product
http://www.omega.com/pptst/OB-100_OB-200_OT-200.html
A thin film of the OB-200-2 and that 2oz should go a long way.