We're just about a month out from the launch of Half Life: Alyx on March 23rd, and like so many other things, it is seeing some impact from the coronavirus outbreak. According to a statement given to RoadtoVR and UploadVR, Valve still plans to restock its Index VR headsets ahead of the game's release. However, over the next few months the company says "we will have far fewer units for sale during the coming months compared to the volumes we originally planned."
You can still sign up for a notification when more headsets are available on the Index's Steam page, which has listed the headsets as out of stock for several weeks.