There's a company called Arctic Silver that makes several heatsink compound solutions. One of them was actually a two part heat sink epoxy you can use to glue a heat sink to a chip.
http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm
http://www.arcticsilver.com/arctic_alumina_thermal_adhesive.htm
The only place I know off the top of my head that carries it is Gigaparts, but it's cuz I used to work there
http://www.gigaparts.com/store.php?action=profile&sku=FN0046
http://www.gigaparts.com/store.php?action=profile&sku=FN0082
I'd shop around and see if you can't find a better price first though. You might even find a local store that sells a similar product.
Whereever you get it from, make sure you're buying the two part compound, not the stuff that comes in just one tube. The stuff that comes in one tube is just thermal grease, and has no adheasive properties.
edit: Obviously, you're going to want to completely remove all of the thermal tape from the bottom of the heatsink before you do this. Also keep in mind that this stuff is EXTREMELY permanent, so be careful.
Edited, Sep 30th 2006 at 12:17pm PDT by Usagichan