looking to buy a new battery ep500 for my old sony sk17i phone

Hi,

I have the old sony xperia slide phone - model: SK17i. I was just checking old stuff in my home and found this phone which my mom kept since many years haha. Now it does not charge and ofcourse I think the battery is dead. So I am looking to buy a new battery and try my luck. The battery is EP500. do you think it would work? and any suggestions from where to buy? I found one on realkart. But idk if these websites can be trusted?