Gomadic High Capacity Rechargeable External Battery Pack suitable for the Sony PHA-3 USB DAC Headphone Amplifier
CEntrance HIFI-M8 V2 Battery-Powered Portable USB DAC HIFI-M8 V2
Amazon.com: ILIWIWY Hi-Fi Headphone Amplifier Buit-in Power Bank Portable 3.5mm Stereo Audio Out Powered by Lithium Battery Headset Support GAIN/BASS for Android phone/iPhone/iPad/MP3/MP4/Laptops and PCs, etc. : Electronics
The 3 Best Portable Headphone Amps With Built-In DAC of 2023 | Reviews by Wirecutter
iFi Micro USB DAC Headamp Open Box
CEntrance HIFI-M8 V2 Battery-Powered Portable USB DAC HIFI-M8 V2
iFi Audio micro iDSD Signature Desktop/portable USB DAC/preamp/headphone amplifier at Crutchfield