I don't know where is Lord Vishnu's Vaikuntha sea. Is it on Earth or not?
Vaikuntha means a place where there's no kuntha (worries/suffering). So definitely this planet can't have vaikuntha.
As far as locating the same is concerned, best of luck but unless you've your kundalini awakened and raised, you can't locate or experience Vaikuntha.
As per the scriptures, in Srimad Devi Bhagavatam:
So there are endless Brahmâs, Visnus, and Mahes’varas. In every Brahmânda, there is Brahmâ, Visnu, and Mahes’a. Each Brahmânda extends from Pâtâla to the Brahmâloka. The abode of Vaikuntha is higher than that (i. e. it is situated outside of Brahmânda), again the abode of Goloka is fifty koti yojanas (50 x 10 x 4 x 2 million miles) higher than Vaikuntha. This Goloka Dhâma is eternal and real as S’ri Krisna is eternal and real.