Amazon.com: Mobi Lock 3.5mm Plug to 6.35mm Socket (Pack of 2) 1/8 to 1/4 inch Stereo Audio Jack Adapter | Connects Devices with 3.5mm Port to Your Amplifiers, Guitar, Piano, Speakers &
Sennheiser Genuine Screw On Headphone 6.3mm Adapter - The Disc DJ Store
Sennheiser Cable Adapter Female 1/4" 6.3mm to Male 1/8" 3.5mm Plug - Newegg.com