Because of Yuneec's history of not being reliable in e-mail communication, I would call them at
their main sales number... (844) 343-9966... just because a part is not listed on their site, does not necessarily mean it cannot be ordered.
It is an Li-on not a Lipo. It is specific to the grip and they are as rare as hens teeth, (right next to Unattainium on the periodic table), I doubt you will find one. You will most likely need to replace it with a Lipo that will fit. However unlike the Li-on, you cannot leave the Lipo charged up all the time.