[Fast Co.]

Here's a link to a site that has a massive amount of corporate graphics from all around the world in .ai and .eps format. Most are modern, but there are a good deal of vintage graphics on here too. The most difficult thing is to determine what graphics were in use for the time you are trying to portray. www.brandsoftheworld.com. I've copied thousands of files from this site during the past several years, but it is far easier to share the link. If you have a graphics program such as Adobe Illustrator that can handle vector files then this site is a veritable gold mine. 
Steve