I’m using this. Had it connected during a 3+ hour stream and the internal battery on my A7SIII never lost a single percentage point.

USB C Power Bank RAVPower 30000mAh 90W

https://www.amazon.com/dp/B08MQ49GSM/ref=cm_sw_r_cp_api_glt_fabc_MQM59HDA057E3VMBDH32?_encoding=UTF8&psc=1

Does not come with a charger to recharge the battery. So I also picked up this to maximize my recharge speed:

USB C Charger RAVPower 65W Fast Wall Charger

https://www.amazon.com/dp/B08MWG612F/ref=cm_sw_r_cp_api_glt_fabc_JN455G19T3JG0SR1Z9XM?_encoding=UTF8&psc=1