Be prepared to spend some money to purchase a test! Prices run from $25 to $100 or more for a single test.
If you know the exact title of the test, a quick way to find the publisher's contact information is to do a Google search using the title of the test. Otherwise, you can check these sources:
these books don't have tests in them;
list and describe tests and give you contact information for the publisher.
The Educational Testing Service's TestLink contains a test collection.
To purchase a test from a publisher:
To purchase a downloadable test:
You can get the downloadable tests for the years 1987-2004 on microfiche for free.