Availability of psychological tests and measures depends on whether they are published or unpublished, as defined below:
Published tests are commercially available for purchase. These measurement instruments have established validity, reliablility and norms and typically come with test manuals and testing protocols. In many cases only qualified or professionally trained individuals can purchase copies.
Unpublished tests are found in the scholarly literature of psychology and have typically been developed by university researchers or other professionals, government agencies, or nonprofit organizations. Copies of these tests may sometimes be found as appendices to journal articles, dissertations, books and other research reports. While access to these tests is not restricted, ethical conduct requires that these tests should be used only with the permission of the instrument's author.
For more information on using PsycTests see http://www.apa.org/pubs/databases/psyctests/index.aspx
Other ways to find instruments is when they are attached to aticles, dissertations and reports Here are some databases which regularly have instruments. Also, check the databases in your field for instruments attatched to publications.