Sump pump battery replacement for IEB 12-120

So my sister had Perma-seal do waterproofing and install a sump pump in her basement I believe 8 years ago. The battery is dead, and needs to be replaced.

I can't seem to find any information about the battery besides the make and model, which is an IEB 12-120. I also can't seem to find one for sale outside of eBay.

My question is simply does she need to get the same battery as a replacement, and if not, what are compatible replacements? If she needs to get the same battery, where can they be purchased?