Kinect stock issues started as soon as retailer started taking preorders. Kinect preorders were over allocated and after the launch date, stock started to run dry. Today Kinect stock in the UK is very tight. For Microsoft this is the first real stock shortage they've seen since the launch of the Xbox 360 console in 2005. However early indications suggest the stock issues for Kinect are going to be far more severe.
If you want to get your hand on Kinect before Xmas, you're going to need to use an online stock checker or stock locator. These sites scan retailer site for stock changes and tell you where you can buy Kinect when it comes in stock.
This following website helped people find stock of the Xbox
360 when it was launched in 2005. They now have a Kinect stock
checking page that will help you find Kinect in stock.
Kinect Stock Locator
Kinect stock locator, Where is Kinect in stock?