Andrew,
You can get the heat sinks at Digi-Key 1-800-344-4539 part #HS157-ND
$4.10  size 1.89"L x 1.89"W x .600"H  comes with clips to install it.
But if it was me I would get a $12.99 small fan from Radio Shack
and install it where it could just blow at the cpu instead...Sam