Instructions
Decide if you are looking for authentic vintage cookie cutters or vintage style and shapes. Vintage style cookie cutters are a little easier to find and they tend to be new so you can use them with all your favorite cookie recipes. Check out Memory Works for a great selection of vintage cookie cutters.
Check out local kitchen and antique stores to find cookie cutters. This is a great item to look for at estate sales too. Storage auctions can also be a good idea. Where there is old and antique, there is kitchenware and cookie cutters.
Shop online. If you are looking for vintage style or authentic vintage cookie cutters you can find both on the web. Check out the All Vintage Store for great authentic cookie cutters and the standard auction sites, if you don't mind used.
Post an ad in your local paper. A lot of collectors use this method and it seems to work well. Sometimes people don't realize they want to sell something until someone asks to buy it. You may even try your luck at Free Cycle, a free exchange community operating via Internet in most towns. Simply list what you are looking for on Free Cycle and wait for offers of free stuff to come your way.