Many sites such as Jigsaw, Lead 411, and others charge a monthly fee. Also, LI InMail can be expensive.
Try Dun & Bradstreet (DNB.com) to buy email addresses with one time fees instead of monthly subscriptions. I get them for free using an automated combination of tools that allows me to target specific people. If that's something you want, request a 15 minute call, which will be enough time for me to walk you through the set up.