The only way to get the gold version of the Google Nexus 6P is to get it in Japan; however, that might change soon. According to the latest Nexus rumors, Google might be getting ready to sell the gold version in the US as well.
That's not the only good news regarding the device. According to the source of this intel, Google may start selling the Nexus 6P in Best Buy as well (just as they currently do with the Nexus 5X). If they decide to do both at the same time, then that would be a nice bonus for folks who would want the gold version, and want to play with the phone before they buy it. We will keep an eye out for official confirmation.
Source: 9to5google