This Movek myMix personal monitor mixer offers great functionality. Note that it doesn't come with a power supply, but can be powered through PoE. There's a known issue where the main knob cover is missing, yet the knob still works perfectly.

Using this Movek myMix personal monitor mixer is easy. First, since it doesn't have a power supply, connect it to a PoE source to get it up and running. When you're using the mixer, even though the main knob cover is missing, you can still turn the knob to adjust the sound. Be careful not to apply too much force on the exposed knob. As for maintenance, keep it in a dry and clean place. Wipe it gently with a soft cloth if it gets dirty. If you notice any other problems, contact customer support.