Many sites such as Jigsaw, Lead 411, and others charge a monthly fee. Also, LI InMail can be expensive.
Getting exact company emails is always something a lot of people are looking into. What I would suggest is trying to get the email address of somebody else within the company (maybe you have a friend there) or start searching for people in the company. A lot of companies follow a simple rule for creating email addresses:
etc. As soon as you know the name of one of the employees and start searching for combinations like this in your search engine of choice, you are bound to find a hit somewhere confirming how the email addresses are formed at that company. Based on that information you can figure out yourself what the email address would be of the person you would want to email ;-)