So, according to the Overlord in Ninjago Rebooted, the remains of the 4(8) Golden Weapons are the only remnants of Golden Power ever since Lloyd gave his up.
However, in the filler season prior to the final battle, we saw that Ninjago holds a locations known as the Golden Peaks.
The Golden Peaks had power enough to merge the energies of the original four golden weapons together into the Mega Weapon.
The Golden Peaks are said to be the place where the weapons were forged in the first place, so I have to wonder, do they possess a source of power?
Another possible theory I have is that The Golden Peaks possess so much Golden Power that even a being like the Overlord could not control.