(ad:) Hardware Store Liquidation, Decatur AL, **February 2023** - Shelving, several heights, 16" or 22" base deck!!  paint shakers, widespan racks and MUCH MORE!!! (click here)
(ad:) Grocery store equipment sale, Atlanta GA, **February 2023** - Shelving 6 and 7ft tall, 22" base!! walk in freezer, 2, 3 door freezers and MUCH MORE!!  (click here)
Birmingham, Mobile, Huntsville, Montgomery, Tuscaloosa AL
Honorable mention to the the Kent Corporation, for manufacturing shelving in America for almost 60 years!
The Kent Corporation - (website)
(Birmingham, AL - gondola manufacturer)

Then go out of state to nearby cities like Atlanta, Nashville, Jacksonville and  New Orleans.
Your nearest used dealer is in Atlanta ,  then you need to jump to Florida's large market or Texas for (a lot of) dealers.

Alabama lacks the presence of a used dealer or major store fixture liquidator, but fair shipping lanes to dealers and closeouts might help compensate for this drawback.

Check out of state to nearby cities like Atlanta, Nashville, Jacksonville and  New Orleans.
If you can't find it in Alabama, try:

Georgia

Florida

Texas

Michigan