In the U.S., at least, AT&T may be the best bet to score AirPods online before Christmas, as Apple and a number of other vendors are now listing post-Christmas dates for shipping.
Apple has long had trouble keeping up with demand for AirPods, often taking weeks to ship. Availability has improved significantly within the past few months, thanks to increased production by Apple, but the holiday crush is presumably taking its toll.
With the exception of Amazon, all of the above vendors may potentially have units in stock at their physical outlets, varying from location to location. That inventory is likely in short supply.