Amazon.com: Stellar Labs Inline Volume Control for 3.5MM Headphones,Black : Electronics
Headphone attenuator – Essential scrap
Headphone attenuation adapter | DIY-Audio-Heaven
Amazon.com: iFi Ear Buddy Audio Attenuator Cable for Headphones and IEMs Compatible with 3.5mm Headphone Jack - Travel Kit Includes Accessories : Electronics
Headphone attenuation adapter | DIY-Audio-Heaven
Headphone attenuator – Essential scrap
Ear Buddy by iFi audio - Headphone Optimiser and Travel Kit
Amazon.com: iFi Ear Buddy Audio Attenuator Cable for Headphones and IEMs Compatible with 3.5mm Headphone Jack - Travel Kit Includes Accessories : Electronics