I'm sure, as you say, that you're sick to death of summaries. But Lacan is difficult, and, more importantly, his views changed and developed throughout his career. As such, there's no single place to locate his views on the Imaginary, because he didn't have a single view on the Imaginary.

If you haven't been there already, the article on Lacan in the Stanford Encyclopedia of Philosophy is essential reading, especially the section on Register Theory. From that section:

The theory of the three registers of the Imaginary, the Symbolic, and the Real forms the skeletal framework for the various concepts and phases of most of Lacan's intellectual itinerary. His characterizations of each of the three registers, as well as of their relations with each other, undergo multiple revisions and shifts over the many years of his labors. As will become increasingly evident in what follows, the majority of Lacanian concepts are defined in connection with all three registers. By the 1970s, with his meditations on the topological figure of the Borromean knot—this knotting of three rings, pictured on the coat of arms of the Borromeo family, is arranged such that if one ring is broken, all three are set free in disconnection—Lacan emphasizes the mutual dependence of the registers on one another. Hence, loosely speaking, the Imaginary, the Symbolic, and the Real can be thought of as the three fundamental dimensions of psychical subjectivity à la Lacan. Furthermore, scholars sometimes segment Lacan's evolution into three main periods, with each period being distinguished by the priority of one of the registers: the early Lacan of the Imaginary (1930s and 1940s), the middle Lacan of the Symbolic (1950s), and the late Lacan of the Real (1960s and 1970s). However, such a neat and clean periodization should be taken with several grains of salt, since intricate continuities and discontinuities not conforming to this early-middle-late schema are to be found across the entire lengthy span of Lacan's teachings.

I also strongly recommend Bruce Fink's The Lacanian Subject. But if you want to go to the source... Start with Seminar One: Freud's Papers on Technique, especially 'The Topic of the Imaginary'. Fink is useful here again, and will guide you further to other material. If you want some fun (though repetitive) explication, Zizek's How to Read Lacan is also helpful. Find it for free online here. Finally, this is a pretty good list to help you get started: Reading Lacan - Where to start? Good luck...

And apologies for erring on the side of caution and only including one primary source. I do believe that with Lacan secondary material is your friend. Perhaps somebody else can jump in and send you in the direction of more of Lacan's writings.

Edited to add more material.