Look at the most recent volume of the Standard Directory of Advertising Agencies; another print source is known as the Advertising Red Book. 

Try looking at Hoover's Academic Pro

• Select 'Build a List' located next to the search box

• Expand the Industry tab and under 'Add NAICS Code' enter 54181 and select Add Criteria

• Then, enter 541810 and select Add Criteria
• Click View Results

Recommended: choose States from drop-down menu; then type the name of the city in the City search box; or type the desired zip codes in the Zip Codes search box.