to be safe go those chain like Fortress, Citicall, Broadway, etc...
got a few good shops around Mongkok for example, Tin Cheung, Wing Shing, DCFever, etc...
skip those shops with Neon Lights saying Tax Free and sometimes Sony... those shops operate like Lucky Plaza / SLS... ;p
the main concern is still, the 100+ SGD savings versus the trouble to walk around trying to get a shop which got stock (i highly doubt there will be enough stock in shops as Nikon normally don't build much for new products)... you friend might be wasting his precious hours running around...