When they close or remodel a store, Walmart often sells off their used shelving to the public.

When ANY retailer closes a store for almost ANY reason, they want to keep it as quick, quiet and orderly as possible.

"Closing"..."Going out of business"...this isn't the best public image. It could affect stocks.

No retailer really wants to advertise this, Walmart included.
Some of Walmarts supply appears to come from Marmon Holdings(a Berkshire Hathaway company).
The Marmon group lists many fixture brand names in their network, both in, and out, of the United States. One gondola brand they offer is LA Darling.

Marmon Holdings also includes Unarco (pallet rack).

LA darling supplies Walmart with gondola, but I doubt that's exclusive in all stores.  Might be worth checking if you need used parts?