External battery for Sony a7siii

I'm trying to find an external battery for the Sony a7siii that will fit into the nauticam housing. I found one for Sony a7sii :https://www.backscatter.com/Zen-External-Battery-Pack-for-A7II-Cameras-17414?_ga=2.267465550.1551494561.1623651297-1998485019.1623651297

but since the new camera uses USB-C that one doesn't fit. Any ideas of a small USB-C battery that might work?m I currently get about 2 hours 40 minutes of continuous video at most, and Ideally I would like to at least double that. Any ideas are welcome!

You could Look around at the various USB-C power  banks on offer, you want a USB-C that is PD rated.  I found a credit card sized one:

https://www.aukey.com/collections/power-banks/products/aukey-10000mah-ultra-compact-usb-c-portable-charger-with-20w-pd

You could use a credit card to see if it's likely to fit?

Hello Ichtyologist,

I am looking for the same, did you find a good solution? When I was on A7S ii i used this battery than could be insert in the trigger flash location https://www.backscatter.com/reviews/post/Nauticam-A7II-UnderwaterExternal-Battery-Pack.

With this one I could dive for up to 5 hours, and use it for long rebreather dives, but I didn't found any replacement for my A7S iii.

I keeep my post uploaded if I found something good