I don't know about you but the cost for the Sony NP-FZ100 Battery is outrageous. $78 on Amazon, even third party batteries sell for $50+ on Amazon. So much for the Sony Tax...

I decided to take a risk and see what Ebay had to offer. 

The seller "fucotter" on Ebay had "Original Sony NP-FZ100 Battery" selling for $32 with postage. I bought one...and sure enough I can't tell the difference between it and the battery that came with my Sony A7III...so much in fact I bought another. 

Maybe they are factory seconds, I don't know, but they give as much charge as the original camera battery. So you decide...