After Valve published "Half-Life: Alyx", sales of Valve Index increased enormously. The VR headset sold out very quickly in many places and it looks like Valve still can't keep up with production.
The page "RoadToVR" analysed 31 regions and countries in which Valve Index is available. And the result: the VR headset is still sold out in 30 of 31 regions/countries. It is only available in Japan. In response to the massive demand, Valve has apparently revised its Index page to make it easier for customers to find out when the VR device is back in stock.
In a statement, Valve said: "We are working hard to produce more units to meet the high demand. Our goal is to be in stock before the release of Half-Life: Alyx." However, it should also be noted that Valve Index is not necessarily required for "Half-Life: Alyx". The shooter, which will be released in March 2020, can also be played with HTC Vive, Oculus Rift or Windows Mixed Reality.
Source: RoadToVR