The following information is from a number of sources. There are also different opinions so I am posting the information with its source. Be reminded that in many communities, there is not a problem with chometz achar Pesach in the local kosher store whose chometz has been sold by the local vaad or rabbi. (Information updated April 20, 2020.)
Shop Rite Supermarkets and Price Rite: Rabbi Elazar M. Teitz sold the chometz.
Jethro/Restaurant Depot: The Kof-K has sold their chomets.
C&S Wholesale Grocers': The Kof-K has sold the chometz ahead of Pesach. of C&S Wholesale Grocers', a Jewish owned food distibutor that supplies groceries to thousands of supermarkets across the United States. C&S owns Davidson Specialty Foods that distibutes kosher and ethnic foods.
(Please note that this does not apply to the individual stores but
rather to the supplier/distributor known as C&S Wholesale Grocers.
Individual stores require their own Chometz sale if they have Jewish
Information on purchase of chometz in various locations