Amazon.com: UGREEN 6.35mm 1/4 Male to 3.5mm 1/8 Female Stereo Headphone Adapter Audio Jack Plug Gold Plated for Speaker Headphone Guitar Digital Piano Amp, 2 Pack : Electronics
Adapter Brass Fittings at Lowes.com
Husky 3/8 in. Female to 1/4 in. Male Drive Adapter HADPTR3814 - The Home Depot
Barrel EXTENSION, Threaded Barrel Adapter 1/2-28 to 1/2-28 TPI