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
M6x1 (m) to 1/8" NPT (f) Adapter for Grease Fittings – LockNLube
3/8" NPT Female to 1/8" NPT Male Brass Pipe Adaptor/Adapter Straight Reducer/Reducing Coupling Male to Female: Pipe Fittings: Amazon.com: Industrial & Scientific
Brass, 3/8 in x 1/8 in Fitting Pipe Size, Reducing Adapter - 1DFY6|6-2 RA-B - Grainger