Where to buy Japanese cards?

Hi all, I'm a new collecter based in Ireland. I've been collecting Surging Sparks to date, and I'm excited for Journey Together. However, I watched a YouTuber open some amazing cards from a set called Heat Wave Arena earlier. The cards in that set are just so much cooler than any others in my opinion.

I was wondering if someone could give me guidance around where to purchase Japanese cards? I've tried Amazon with no luck. My local card stores barely have stock of Surging Sparks nevermind Japanese cards.

Any info/guidance would be greatly appreciated from a new enthusiast.

Thank you!