Jones Stephens - Drain, Waste & Vent Cleanout Test Tee with Cleanout Plug: 4″ Fitting, Hub x Hub x FIPT, Polyvinylchloride - 96872197 - MSC Industrial Supply
NIBCO 4 in. PVC DWV Spigot x Cleanout with Plug Adapter Fitting C4816HD4 - The Home Depot
4" Countersunk Cleanout Plug - RJ Supply House
Charlotte Pipe 4-in PVC DWV Cleanout Plug in the PVC DWV Pipe & Fittings department at Lowes.com
Oatey 4 in. PVC Snap-In Cleanout Assembly - Sink And Drain Equipment - Amazon.com