Looks like many of the small to mid size online bullion dealers are flat out of silver, while the larger ones have limited product selection and wait lists for many items.
Yet the price of silver continues to fall ( up, however the past couple of trading days)
Here are some potential explanations from Is there a silver shortage?
-coin demand is but a small part of overall silver demand
-retail vs whole sale shortage
-supply is keeping up (or has until recently) with demand