I'm going to throw in a couple of cents, since I don't think Arctic will be very cheap bought as a one-off. But I may be wrong. You definitely will not need that level of heat conductance on the top of a ceramic chip package, let alone a plastic one.
You can do two other things: As Plasma suggest google for "Thermal Adhesive", many cheaper types exist, as an example of what I use, bought in bulk, for not-so-heat-critical things:
Farnell Listing for Fischer Thermal Adhesive
May also be obtainable through easier mediums. This does have the disadvantage of needing a precise measurement tool for the stuff. If you need a small drop mixed, you're looking at miligrams of hardening liquid.
But, what you can also do is much simpler and household-budgetty:
Take a drop (or small stripe) of thermal compound on the heatsink, press it onto something made of glass (bit of alcohol and an old cloth will clean it off, no worries) and see how much it spreads. On glass with high pressure (don't break your glass!) it will spread more than on a chip with a rough surface in comparison, but not by 50%.
Now find the drop that will cover about 80% of your heatsink.
Once you have found the drop-size you need (and over time you will get better and better at it in one go if you need to do it often):
Apply the drop-size you need, put some high-strength glue to the small bits that you expect won't get covered. Such as brand name super-glue, or usually better with plastic dips that get hot: "heat proof" (upto 100degrees C is fine) epoxy or silicone.
Press on and hold in place with a decent clip until the glue is fully hardened.
Done, preso-magnifico and you will likely be using the glue elsewhere often enough to validate its purchase.