You might want to check out www.elitefourum.com/t/japanese-unlimited-e-series-1-cards-base-expansion-pack/16426/1. Whilst these cards are very hard to track down, the majority of people don’t know about them and when they do show up they often sell for the same as their mass-produced 1st edition counterparts.
With the exception of Ponyta (mass produced), Charizard and Pichu (distribution unknown but likely not much higher than 300), the other cards which are available have an estimated print run between 8 and 50, making them some of the rarest cards in the hobby.