Like TDAWG says, PepBoys or many other places like AutoZone, Discount Auto Parts or even go to the OPTIMA WEBSITE and search for a dealer.

Pretty much all you need to do is decide is you want the Red Top or the Yellow Top and make sure the terminals are oriented the same as yours. They'll probably tell you it won't fit, but it will as long as the terminals are the same, which are standard. Where you go might have a reversed-terminal on hand and try and shove it off on you to get it out of inventory. The Red Top is the most common and the Yellow (deep cycle) would be good if you plan on having a monster stereo, lots of lights and maybe a winch.