No, you don't need to unwrap thousands of Wonka Bars to get one.
Nintendo loves to mock those who have bought their products early by coming out with new colors after most of the people have settled with one. This time, if one of the dozen or so of available GBA SP colors haven't caught your eye as of yet (Cobalt, Platinum, Flame, Onyx, Famicom, Pearl Pink and Blue, Gundam Red...), Nintendo figures this latest Japanese shade will be impossible to overlook.
The New Gold GBA SP is currently only available exclusively through Toys 'R Us Japan, for the standard price of ¥11,999 ($110-ish). There isn't any indication if this color will or will not come to the States at the present time, though.