Hi-Fi Headphone Amplifier Portable Headphone Amp 3.5mm Stereo Audio Input Out Buit-in Power Bank 3000mAh(3v) for iPhone6, iPod, iPad, MP3, MP4, Computer, etc. - Walmart.com
Amazon.com: Lavaudio Headphone Amp Portable Desktop DAC 768kHz/32Bit and Native DSD512 USB Type-C Hi-Res Stereo Headphone Amplifier 3.5/4.4mm/Coaxial/Optical Out for PC/Laptop/Smartphones/Speaker Home Audio DS400 : Electronics
Singxer Sa-1 Headphone Amplifier Fully Balanced Discrete Class A Amp/preamp Sa1 Support Xlr/6.35mm/4.4mm Multi Interface - Headphone Amplifier - AliExpress
16-300Ω Mini HIFI Headphone Amplifier Portable Earphone AMP 3.5mm with Audio USB Cable - Walmart.com
Neoteck Ma400 Headphone Amplifier For Xlr Microphone & Audio Signal With 6.35mm & 3.5mm Headphone Outputs Headphone Amplifier - Headphone Amplifier - AliExpress
Lehmann headphone amp clone on aliexpress | diyAudio