The Theatre Arts Department keeps a small collection of scripts on hand for classroom use, acting exercises, etc. Check with them for further information!
Wilson's Play Index (REF PN1625 .Z76) has an index for locating plays by the number and gender of the characters involved.
For a free online tool, try:
Pfau Library has a large number of scripts from contemporary and classic plays!
Use OneSearch to locate them.
Do a simple search for the title of the play.
Imperceptible Mutabilities in the Third Kingdom (appears in an anthology of the author's works)
If the play's title is short or consists of common words, add the author's name as a keyword. For example, to find Beth Henley's "Abundance," try the search: abundance henley
The journal "American Theatre" sometimes includes the script of a short, contemporary play. The site below provides an index to titles and authors covered.