As you read the secondary sources on your play, keep an eye out for any mention they make of important or controversial productions. These might be worth following up on. Take notes on date, location (city and house), and the director and major actors. Also note if they say why the production was significant.
"Stage History" Subject Search in Primo - Depending on how deeply you want to dig you could search for your author along with this subject heading. This will not bring up reviews but more analysis, but it could point you toward particular productions.
Especially for recent productions, Google can be a powerful and easy place to locate reviews. Here are some tips to make these searches more effective.
Primo - This engine can be a good place to start because it indexes a lot of the library's newspaper and magazine full-text collections. Always narrow down to your date range to the year of the production you are looking for and consider adding a keyword for the director, major actor, or house.
IBTD indexes and in many cases provides full text to many of the major review sources for theatrical productions. Searching here for your play will automatically eliminate many of the smaller productions you are less interested in.
To just see production reviews, structure your search in this way:
Skim the results for the names of notable houses, directors, and/or actors. Once you have identified a production you are interested in, conduct a new keyword search for just that production and limit it to reviews.
Looking for reviews of British productions? If you spot a citation for your play production in the Theatre Record, this is worth placing an InterLibrary Loan request for because this will give you several reviews for the same production at once.