Mono

TISINO 1/8″ TRS Stereo to Twin 1/4″ TS Mono Y-Splitter Cable, 3.5mm Mini Jack Aux to Quarter inch 6.35mm Jack Stereo Breakout Wire – 3.3 ft

Headphones

Jabra Evolve 20 UC Mono Wired Headset - Calls and Connectivity

Wearable Technology

6.35mm Audio Adapter Pack with Screw Terminal for AUX Headphones

Headphones

Professional Mono Earbud Palms-Free Works for Kyocera DuraForce Professional 2 with Constructed-in Microphone and Crisp Clear Protected Audio! (3.5mm / 3.5ft Size Cable)

Headphones