Use regular headphones & mic with your intercom beltpack
Point Source ADP-PHX4F Adapter Cable with 3.5mm TRRS to 4-pin Female XLR - ProAudio.com
Amazon.com: Rugged Carbon Fiber Behind The Head Headset and Adaptor Cable for Intercoms – Features 5-Pin to Off Road Coil Cord and Volume Control Knob 3.5mm Input Jack : Electronics