What is the best lipo battery for around $50 for the traxxas 2wd xl-5 slash.?

I am going to be racing me traxxas slash in the stock SC cl. We are allowed to run 7 cell NIMH or 2 cell Lipo. I am going to running lipo. I have a titan 12 motor and the xl-5 esc. Whats is the best battery I can buy for $50 I want going to buy 2 of them. I have an onyx 230 charger.