I looked at all the Oculus battery accessories out there and they're all terrible; even the official ones. 1.5 hours, 2 hours, etc.It's never gonna be REALLY mainstream until they sensibly reduce weight and size and a big improvement on the battery life.
They are just too bulky, uncomfortble, easily sweat inducing to make a breach on the hearts of the casuals or anti-vr people.
And this comes from a guy with 2 vr device that probably gonna buy a psvr2.
Literally all you need is a $50 multi-purpose power brick charger. If you ever feel like playing for longer than 2-3 hours, then just put it in your pocket and run the cord under your shirt. Lasts probably 8 hours on top of the normal 2-3, and you don't have to wear it on your head. All the accessories seem like a waste of money to me.