We will be staying near the Louvre July 8th-11th. My understanding is there are a couple of theaters near our rental apartment.
Try Time Out Paris
We always use classictic.com.
My experience with Classictic was not a happy one. We bought tickets for a concert at Eglise de la Madeleine, a concert that did not exist. After many, many weeks of trying, and with the intercession of our credit card company, we finally had our money refunded. After all that hassle we would never use them again.
Try Secrets of Paris. In addition to being a really good tour company their website has a lot of event information.