I pad (7th Generation 128 GB. I’m missing the stand piece in the back of the iPad silver, can I purchase the original gray stand in the back

Apple no longer makes just a back case for iPads.

There are smart covers and smart keyboard covers for the 7th and 8th gen iPad models that protect the iPad screen, but nothing made by Apple any longer to protect the exposed back panel.

There are lots a back cases/full cases and other keyboard cases made for the 7th/8th gen iPad models made by third party case makers.

You can find an abundance of these on Amazon.

Best of Luck to You!

iPad is not suppled with any kind of case or stand. These are accessories.