BrassCraft 1/4-in x 1/8-in Compression x Mip Adapter Fitting in the Brass Fittings department at Lowes.com
LTWFITTING 1/8 in. O.D. Comp x 1/8 in. MIP Brass Compression Adapter Fitting (5-Pack) HF682205 - The Home Depot
RPS Lighting Female 1/8" Mini to Male 1/4" Mono Adapter RS-8610
Amazon.com: VCE 1/4" to 1/8" Adapter, 3.5mm 1/8 inch Male to 6.35mm 1/4 inch Female Audio Jack Gold Plated Adapter for Amplifiers, Guitar, Home Theater Devices, Laptop, Headphones - 8 inch : Electronics
Audio Adapter - 1/4" female to 1/8" male - Stereo TRS | SWAMP
Amazon.com: Cable Matters 5-Pack 1/4 to 1/8 Headphone Adapter (3.5mm to 1/4 Adapter, 6.35mm to 3.5mm Adapter) : Everything Else