http://www.haiyinstore.com/compares....=208+&PID=209+ I'd go so far as to say the 20C pack here will outdo your stocker , but maybe you'd like more power and would get the highest one.
http://hicountryhobbies.com/index.ph...rdubq20c6ijfb4 These are supposed to be excellent packs too.
These may be some of the best "deals"
http://www.hobbyking.com/hobbyking/s...on=1&x=67&y=16
hobbypartz
http://www.hobbypartz.com/98p-60c-5000-5s1p-5555.html
http://www.hobbypartz.com/77p-sl5000-5s1p-20c-5555.html
http://www.hobbypartz.com/83p-5000mah-5s1p-185-30c.html
http://www.hobbypartz.com/83p-5000mah-5s1p-185-40c.html
After seeing the plane and the stock battery it seems like this can be a very aggressive short flight which requires good stuff. I think the highest rated haiyin pack is what I'd use. Nothing says you have to stay at exactly 5000 mah either. This can vary a lot. Good luck , maybe next season I have a plane (and skills) that good,lol.