This page will go over how to make some additional modifications to the boombox. If you’re here looking for how to add/change the songs on the boombox, refer to the Installation Guides.
On the VRCFury version of the prefab find the ‘Armature Link’ component on the BoomBoxSystem object. This component is what’s parenting the holster position to a specific part of you avatar’s armature. You can choose to link this to any other part of your avatar with the Link to Dropdown.
I would also advice changing the size of the holster contacts if you do move it around as they were mainly intended for the back holster and were larger as a result.