I am not sure if I am allowed to put the link here. I suggest you go to ebay and look for seller 100digi using keyword like google nexus 7 battery. The seller is listed as HK but most probably in China.
The battery has not arrived yet so I have not tried changing it. You can google video and it is pretty easy with the right tool. From what I saw from online video it is the same way that I changed the battery for my Samsung Tab S (first generation). When I bought the replacement battery for my Samsung it came with some tools that is useful to pry open the tablet.
So even if this ebay seller dun provide me with the tools I still have the Samsung ones. It would be slightly more difficult if you dun have the right tool. Watch online video and you would understand what I meant.
My samsung also did not hold the charge for long. A fresh replacement battery and it is as good as new now. I gotten so frustrated with it earlier that I threw it one side for almost a year. This nexus tablet is my son tablet. If I can't fix it I may buy either a MiPad3 or Nvidia Shield K1 or even Ipad Mini if he surprises me with his mid-year exam.
Can you share the link where u ordered the replacement battery? And how do u intend to install the new battery?
My set's battery can't hold charge for long, so suspecting a new battery would do the trick.