Yes Walmart does sell salt pork.
The salt pork in Walmart should be found in the meat section where the other pork meat is sold.
If you cannot find the salt pork in your Walmart store you can ask an associate and they can help you find the salt pork.
Whenever I bought salt pork here at my local Walmart the salt pork was always located in the same area as the regular non salt pork is.
Usually the salt pork is in plain sight even though we may not notice it.
If you've bought regular pork at Walmart then the salt pork should be close by.
Most other grocery stores should also sell salt pork as well.