Or a google search for “fritzing part transformer” which will usually find anything that is out there. The part you want may or may not exist depending on whether someone has made one before (especially if you need pcb view.) A more accurate description (such as the data sheet for the exact transformer you need) is also a useful start, “has 5 pins on the primary and on the secondary side” could describe almost any transformer.
No, you’re not losing your mind … the “search” feature of Fritzing has never been what I would call “straight forward” … I believe there are two different places where you can place a cursor and do a search over on the right in the parts area … and for some reason I always get no results until I do something … which I cant remember at the moment what that is … .but once I do it … I can search all the parts … it’s a little quirky, but I’m, convinced that it makes perfect sense to the developers of the software so I just learn to adappt.