Episode 36: INEARS on the Cheap | MIDWEEK SERVICE -

Prentiss L. Thompson breaks down Personal In-Ear Monitor Amplifier, It is a convenient hard-wired personal in-ear control center with a belt pack that can be used with your favorite headphones, earbuds, or custom-molded professional in-ear monitors Whether you're a keyboardist, drummer, or other musician whose performance keeps you anchored in one spot.
links:
https://www.bhphotovideo.com/c/product/1358427-REG/behringer_powerplay_p2_ultra_compact_personal_in_ear_monitor.html

https://www.bhphotovideo.com/c/product/1069023-REG/whirlwind_pw_1_personal_wedge.html