I found this blog https://zipser2018feb.wordpress.com/under-surveillance/ from someone who reviewed their Stasi file. They were visiting professor of German from University of Delaware. As a visitor from the "capitalist West" of course they had file on him.

He did discover the names of some of this informants https://zipser2018feb.wordpress.com/my-stasi-file/

> The file reveals that there were nine unofficial collaborators of one sort or another who reported on my GDR-related activities and gathered information on me for the Stasi. Three were writers: IME “Dichter” (Poet), Paul Wiens, a well-known, well-connected poet and communist party loyalist [...] Two informants were good acquaintances, a married couple I got to know while living in East Berlin: IMV “Kurt” and IMV “Julia.” [...] There is evidence that two American Germanists, “unofficial sources,” informed the Stasi about my GDR-related activities in the United States. Although they are unnamed, I was able to identify them from the information provided. The file also contains four surveillance reports (one stretching over a three-day period), which were authorized by the Ministry for State Security and prepared by Stasi operatives. In these I have a code name: “Adler,” eagle, the bird of prey.