A:
Sorry, no: the keyboard/power interface to the tablet is proprietary. I have not seen any compatible devices.
However....don't panic. Check out the power settings on the tablet that can extend battery life. For your actual use, you may get longer life.
If you want a system where the tablet is created by folding the unit over, instead of detaching from the keyboard, try a different HP, Lenovo, Acer or Asus system available at Best Buy