Most stores only sell cloth backed disposable adult diapers and not plastic backed.
But there is one brand of in store adult diaper that I know is plastic backed and those are the Depends With Tabs which are plastic backed.
Some Walmart stores will have the Depends Plastic Backed Adult diapers while other Walmart Stores may not stock them.
You can get them shipped to the store though but if you can order online you can get better quality plastic backed diapers such as northshore supreme poly backed diapers or attends poly diapers.
Abuniverse also makes and sells plastic backed adult diapers which are much better than depends diapers.