So as a quick update: Korea’s Pokémon Store has original Pokémon products with barcodes like 880 9581 50143 0 (www.pokemonstore.co.kr/goods/goods_view.php?goodsNo=1000002813) - 880 meaning they were specifically made in South Korea - but they also use Japan’s The Pokémon Center Company barcodes like 452 1329 30745 9 www.pokemonstore.co.kr/goods/goods_view.php?goodsNo=1000003864 - in this case the exact same product can be found on Japan’s Pokémon Center Online store at www.pokemoncenter-online.com/?p_cd=4521329307459.
Interestingly the Pokémon Korea store has product barcodes which no longer appear on Japan’s Pokémon Center Online store - I’m not sure if this means they’re Korean-exclusive or if Japan simply no longer stock those items any more.
In terms of scraping the data, I’ve managed to work backwards from 21,000 down to 9,000 and have so far identified 1,670 products. The only product which exists between 9,000 and 11,151 is 9,167 which is from all the way back in December 2009: www.pokemoncenter-online.com/?p_cd=4521329091679. I’m going to go down to 7,000 and if I don’t find anything else I’ll start going for 21,000+ (where I’m expecting to grab at least 6,000 more items).
The names are all in Japanese, so I might try running them all through a translator but I think what I’ll do is just share a Google Sheets list here with the raw Japanese names once I’m done.