I bought 65 grams of Arctic MX-2 a few years ago since I got sick of buying little tubes of stuff. It is not quite as good as Arctic Silver 5, but it is still very very good and is non-conductive, non-capacitive.

It is available on Amazon: http://www.amazon.com/ARCTIC-MX-2-Thermal-Compound-Non-Electricity/dp/B004YITI5M