Sad but yes, I think that the crisis is why there is no longer stock indeed. But there are alts -more expensive of course-, but the end of the game, who was announced more than a month ago now, don't helped. But there seems to be restock anyway from other websites (I think of Nin nin game for example who recently restocked set 18, but it's no longer available now!) So, maybe Amiami will be restocked when the pandemic will end, but we can't be sure about that sadly.
As fore advices, as long as no one knows if Amiami will be restocked, maybe you should try to buy them on other places if you're familiar with proxy service, that's more expensive but there's large stock on Amazon Japan or Rakuten japan too.