I believe this is what the user is talking about:
http://www.amazon.com/Extended-Battery-Hyperion-Compatible-International/dp/B00NLJAEJO/ref=sr_1_1?ie=UTF8&qid=1444743293&sr=8-1&keywords=hyperion+battery+lg+g3
Too bad it adds a bit of bulk to the phone.
Also looks like it loses NFC capability, which is a deal breaker for me.