I'd like to buy a dual battery mod for a good friend of mine for Christmas. He really needs a dual battery mod (only has one mod and its a single). He mainly vales 40-50 watts. I'd like something that's 55 bucks or less and then hopefully get a discount code. One thing I know is he is rough on his possessions so I need something that is tough. Main criteria is tough, dual battery and 55 bucks or less. Thanks for any recs.