The Switch has been hit hard by shortages the world over, and that has a lot of customers turning towards Switch Lite. The situation is especially bad in Japan, where even the Switch Lite is getting hard to find.
It seems the launch of Animal Crossing: New Horizons was just too much for people to resist the Switch, and they've gone after the Switch Lite in droves. The Turquoise, Yellow, and Gray Switch Lite options are all sold out at Amazon Japan, Rakuten Books, Bic Camera, Yodobashi Camera, and 7net. The My Nintendo Store still has some units, but those are sure to disappear quickly.