This brand is pretty popular: https://www.amazon.com/Nano-Mount-Battery-Camcorders-Smartphone/dp/B07VY96HNK/

But the $/Wh ratio is quite high compared to the generics I use: https://www.amazon.com/REYTRIC-13400mAh-Compatible-Camcorder-Broadcast/dp/B09B3B93GF You'll notice 10 different brands on Amazon have the same case and slap a different sticker on them.

I'd rather use a battery plate or dummy battery before I pay 4x the price for the same amount of power.

The Smallrig has gotten raves from YouTubers, but not enough long term reviews for me to trust them yet. It seems great for run and gun setups, but I usually do long shoots, so I'd rather have a plate and just swap the batteries, rather than swap 5 cables.