This mount is designed for the Anker Powercore II 10000 (longer battery packs might work but I don't guarantee it). This fits the more generic-looking Quest 2 halo straps (the one in the picture is this one which I based the mount design on). Pretty much any halo strap which has a back designed like the one in the picture should fit. It will not fit more elaborately designed ones like the BOBOVR M2 or M2 Pro (although the M2 Pro already has a battery pack so there would be no reason to use this mount).
Both models are already in their optimal printing orientation.
Clip the two halves onto the halo strap, slide the battery pack into place, and secure it in place with a long length of velcro as I did in the picture and you should be good to go!
In addition to the 3MF files, the project's step file and fusion 360 file is included.
The author hasn't provided the model origin yet.