Unfortunately companies don't always make it easy for nonprofits to get in touch with them.
At Double the Donation we build and maintain a database of companies that match donations along with as much information as we can track down on the program such as forms, guidelines, instructions, etc. Often times we have contact information though that may be to the vendor that administers the company's matching gift program instead of to the company directly.
You can search our demo database at https://doublethedonation.com/hosted-demo/
Within it you'll see whatever information we have about a company. It may help you identify a starting point of contact.