iFi Audio micro iDSD Black Label Desktop/portable USB DAC/preamp/headphone amplifier at Crutchfield
1 Pcs Portable Headphone Amplifier Less Bx2 Plus Earphone Full Balance Hi End Amp Dual Channel Output For Mp3 Mp4 Amplifier - Figurines & Miniatures - AliExpress
Vox amPlug 2 Classic Rock Battery-Powered Guitar Headphone Amp AP2-CR