In requesting information and a possible model the battery mount that the company Globular Cluster had developed for their Headstrap for the Quest 3 called CMQ3. They were very kind and provided me the step file for theirs that fit an Anker 5000 mah battery. I personally want something with higher capcaity than even a Bobo VR battery. I already have a 24,000 mah battery from Shargeek and am starting with it. If you wanted you could take this and cut out the geometry for my battery and model in what you need.

I don't have the headstrap yet so can't test fit it, but the part for fitting the battery I know will as I've already modeled and printed a brace that allows plugging in a Type C cable to the high output port and protecting it from damage from bending and torquing. I thought of that idea when seeing how the Apple Vision Pro headset cable locks into its battery and thought would be ok putting this battery in my pocket. But in practice its too bulky and the long cable gets in the way. So want to try it as a counter weight on the back of the strap.

I highly doubt the hole for the cable with fit a wide variety very well as it needs to be snug to prevent damage. So unless you have the same one (will later upload photos showing which one and is around 0.240 in. (6.1mm) x 0.410 in. (10.4mm) then you will want to download the step file or Fusion 360 file ( upload later as well) and modify to fit you cable. You could just notch it out enough to fit any cable but would be a high risk of damage to the battery port or cable while in fast gameplay.