What exactly are you looking for, in simple terms?
Your brother's drug dealer?
I know you want payback at a time like this, but even if someone here knew, it'd be putting that person in danger by telling. If you're enough of a loose cannon to come on boards and announce this to strangers, you're probably going to be emotional in a confrontation, leading to you leaking the source of your info. This would put your informant at risk.