There are several ways:
#1. Reach out to the contact that you do have, ask them who is the CEO/COO/Director/MP/etc .... then send your contact an email, requesting it be forward to _______________, and that the subject matter to be discuseed is "Private & Confidential"
#2. Spend time and money networking at the b2b shows and building relationships with veterans on the industry and key personel of the company you're interested in.
#3. Look for PRs from the company you are targeting. Very often they quote something from Person at Key Postion of Company XYZ.
#4. File and Serve them a Civil Complaint and dont forget to name the unknown Defendants as John Does 1-100, and see who responds.
Good luck!!!