Adapt is a B2B contact and company database provider across multiple industries. Adapt has 100 million business contacts, including industry-specific company database and contact information such as job title, direct dial, and email addresses.
It's affordable and they seem to be able to find a wide range of contact details. They have a nice Chrome extension which works well.
TaskDrive supports sales and marketing teams by providing personalized lead research, data enrichment and account-based insights.
If you need a very high-touch list building service then this one's for you. You get assigned a researcher who allocates 40 hours/week just to you.