Where Can I Buy A Pump For My Foundation Battery Back-up For Townhome Sump Pump?

Battery back-up for Townhome sump pump? - where can i buy a pump for my foundation

I live in a townhouse and has a sump pump. As I said, what are (our foundations in concrete even when I hear a dog bark more, if I'm in the basement are not sure what that means). We have a semi (Keller gypsum). Is it worth buying a spare battery for our sump pump, if not do our neighbors?