Pomona 6728-2 Standard Sheath Banana Jack to Non-Sheath Banana Plug Adapter, 1.850" Length, 0.395" Width, Red (Pack of 5): Electronic Components: Amazon.com: Industrial & Scientific
4mm 10pcs Banana Plugs and 10pcs Banana Sockets (Black and Red) Jack Connectors - - Amazon.com
Amazon.com: CESS Banana Female Jack Socket - 4mm Banana Jack (10 Pack) : Electronics
Amazon.com: CESS Black and Red Banana Female Jack Socket - 4mm Banana Female Connector Panel/Chassis Mount Soldering Type (10 Pack) : Electronics
Amazon.com: TNP Banana Jack Keystone Insert (Set of 4) - Stereo Speaker Banana Connector Binding Post Snap in Adapter Socket Female Port Inline Coupler for Wall Plate Outlet Panel, 2 Channel Black +