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 May 3, 2019.)
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': Badatz Btzedek Tishpoit 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. Chometz
The following is a link to a list of the top customers on the C & S website:
(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