I've been through similar situations. The "find a lawyer" comments are less than helpful, since you probably don't know where to begin and most lawyers will happily take your money without necessarily having an expedient path to resolution for a small one-person company. So here's what you do: Write to each of your competitors, explain the situation and ask for a referral to their lawyers. You'd be surprised how many…
I, personally, would not risk this approach.