Monoprice 1/4in (6.35mm) TRS Stereo Plug to 3.5mm TRS Stereo Jack Adapter, Gold Plated - Monoprice.com
Amazon.com: ANDTOBO 1/4''(6.35mm) Male to 1/8'' (3.5mm) Female Stereo Audio Jack Pure Copper Adapter for Headphone, Amp, 1 Pack-Black : Everything Else
6.35mm (1/4 Inch) Stereo Plug to 3.5mm Stereo Jack Adapter - Gold Plated - Walmart.com
1/8″ (3.5mm) Stereo Male to 1/4″ (6.3mm) Stereo Female Adapter – ProCAT