Amazon.com: 4" Inch Metal Tee Cap - Round Vent Cover - Galvanized Steel - Indoor and Outdoor Pipe Cover - Dryer Vent Cover - Dryer Duct End Cap - 4In Metal End
3/4" Stainless Steel Cap - Warren Pipe and Supply
4" NPT Pipe Cap 150# Malleable Iron
Amazon.com: 4" Inch Metal Tee Cap - Round Vent Cover - Galvanized Steel - Indoor and Outdoor Pipe Cover - Dryer Vent Cover - Dryer Duct End Cap - 4In Metal End
1-1/4" O.d. 30mm 4x Stainless Steel Round Tube End Cap Push Cover Handrail Tubing Pipe - Pipe Fittings - AliExpress