Hello treez,
The only thing that I know of that may suit your needs, is a heat sink compound that a company
here in Australia sells. The company is called WES Components.
You can locate the product
HERE
When the page has loaded, go to the, "Electronics Components" option on the left hand column.
Click the "Greater Than" symbol to the right, and go through each page until you get to Page 10-35.
When you reach that page, have a look at an item heading: HEAT TRANSFER COMPOUND THAT SETS HARD
The stuff is called, "Platinum Thermal Grease".
This compound sets hard, is not silicone based, but once set, its extremely difficult to remove the item stuck to
it.
I apologize for the poor picture quality, but if you inquire with the company, they may be able to give you
specifications to which may be desirable for your needs.
A word of warning though, this stuff is not cheap.
I hope the above helps.
Regards,
Relayer