For what specific area?I'm looking for similar products at this time, could you name a couple?
Grips are the obvious one of course.
There's an entire market of tethered power solutions.
Its just a replacement battery, just one that doesn't fit. And they haven't verified their claims.
Personally, I trust OEM batteries because they won't fail. But i'll track you down some options really quick. Lets use.... The 5d mark iv as an example.