the 512mb GTX cards are not that rare, I think what you mean is that they are expensive and in some terms... a rip off.
I spray painted my fan/grill gold with cheap spray stuff from Walmart, then I added sparkle to from a sparkle spray that I also got from Walmart. Then I finished it off with an overcoat that you can also find at Walmart, it will protect the surface of the heatsink. This being, so that you are not limited to a company's golden colored heat sink and instead chose the heatsink/fan you want to use. But I only sprayed the fan and protective grill of the heatsink, and not the heatsink since I guess it will just melt off and destroy my mobo. I guess if you were serious, you could get spray paint for cars, which are designed to survive through prolonged levels of heat, because you don't see gold-painted cars melting from the sun's rays.