toshiba laptops batteries

My sister gave me her old laptop because her husband bought her a new one. She told me that the laptop is still good condition but I have to replace its batteries and reminded me to make sure I buy toshiba laptops batteries. So far the unit is still running good but as early as now I am saving so that I can buy a new batteries. It is quite expensive but I guess it is worth it because it is highly recommended by my sister.