They seem to be in stock at the link he gave you. Amazon has numerous vendors with them in stock (I've had good luck buying from Seeed Studio, but not for rpis, YMMV). I bought 3 of them in the middle of covid when there were almost no rpi 3 or 4 SBCs for consumers anywhere on the planet and if you did find on they were 1 per customer. I think I got them from AdaFruit, who have 78 in stock right now. They were and are anything but unavailable.

Oddly, rpilocator doesn't seem to track them, so if that's your definition of "available"...surprise?