I have 2 x Pro Ject Head Box S2 Digital desktop headphone amplifiers.

Details can be found here: https://www.project-audio.com/en/product/head-box-s2-digital/

RRP is AUD $479.00

These are both new, but were not suitable for my needs (I needed an analogue headphone amp).

Comes with Australian power supply, but takes 5V micro-USB, so any micro-USB power supply will work.