We can first search the Wentworth catalog with monologues as keyword, but we get no results. When we search the entire FLO catalog, we get over 1100 results, most of which are at Emerson College Library, which is on Boylston Street downtown. I'll get Emerson's hours for you.
But if you can use something short, you might try our copy of Bartlett's Familiar Quotations located here in the Reference Collection.