Before you start looking for tests and measures, it is important to understand the differences between "published" and "unpublished" tests and measures.
Published (commercial) tests can generally only be used with permission and are typically purchased. Tests and measures covered in the Mental Measurements Yearbook are in this category and include some of the well known tests. While the library can help you obtain information about these measures, we generally cannot get the test itself. To do that you must contact the test publisher/vendor.
Not published (noncommercial) tests are not sold commercially, but rather available via research articles, handbooks or other means. Research articles almost never have the full test/measure. So, you will have to contact the original author to obtain the complete instrument.
For more in depth information you can check out the FAQ from APA (American Psychological Association) or contact your psychology librarian for help.