I'd look up either online or in the ph book Interstate battery's and buy one that has at least a 850 cold cranking amp rating.It will cost you about 90 bucks or so but have a 5 year warranty and a 3 year full replacement warranty with it too.
Hope that helps and best of luck.By the way I find those battery's are one of the best in the world and great for extreme weather conditions etc.Here's a link for you so you can find a local store that sells them.
http://www.interstatebatteries.com/cs%5Festore/