I wish you the best of luck on this search. It had taken me a while to find both the 1st ED and UED versions of Jigglypuff/Wigglytuff from the Blastoise starter deck.
Based on Bulbapedia, the starter decks are also containing pairs of cards based on evolutionary line. In the Venusaur half deck, you could receive Rattata and Raticate, or Doduo and Dodrio.
Otherwise, I did find the 1st ED Rattata and Raticate during my search in 2023 and posted it here (I did not buy it): The New Giant Deal Thread - #348 by sean
I ultimately found 3 out of the 4 Jigglypuff/Wigglytuff cards on Mercari JP. I found the 1st edition Jigglypuff on Yahoo Auctions JP. All through Buyee.