iFi Audio ZEN DAC Desktop USB DAC and headphone amplifier at Crutchfield
Apogee GROOVE Portable USB DAC and Headphone Amplifier Bundle with Audio- Technica ATH-M50x Pro Studio Monitor Headphones | Reverb
AT-HA40USB by Audio Technica — Headfonics
Audio-Technica R70X Professional Open-Back Reference Black Headphones w/ AMP Bundle Includes, FiiO E10K USB DAC and Headphone Amplifier & Slappa HardBody PRO Full Sized Headphone Case (Black) - Walmart.com
iFi Audio GO bar Ultraportable USB DAC/Amp | HeadAmp
THX's tiny Onyx USB-C DAC is $50 off at Amazon
Apogee GROOVE Portable USB DAC and Headphone Amp w/ Audio-Technica ATH-M50x 805676301419 | eBay