HotHardware published Valve Index VR Headset Now Available To Order With One Big Caveat For Half Life: Alyx Fans A quote from the article:

Late last week, we reported that the high-end Valve Index virtual reality (VR) headset would be back in stock this week via the Steam Store. More specially, Valve said that you would be able to order the Index on March 9th at 1PM EST. Well, the Valve Index is available to order now from the Steam Store.

  Valve Index VR Headset Now Available To Order With One Big Caveat For Half Life: Alyx Fans