Above is one such thing, no affiliation what so ever with the listing party, have had several of them, they work great.
Add Blue Circle, Equi=Tech, Furman and Balanced Power Technologies (BPT) to the list. With regard to such products being "top tier", there are more similarities than differences between them all. For one thing, Torus, Bryston and BPT all employ the same "LO-NO/NBT" OEM isolation transformers manufactured by Plitron Corp.
BTW, Cinepro is still in business, with a whole new lineup of products. http://www.cinepro.com/
By their nature, toroidal transformers have a much wider bandwidth than EI transformers, meaning they pass more high frequencies than an EI would, while both will pass the fundamental AC frequency well (60 or 50Hz). The goal of an isolation transformer used as a filter is to block as much of the HF hash as possible, preventing it from getting into the connected equipment, so it stands to reason that a more lossy transformer would do a better job of that.
Not saying a toroid with an interwinding screen won't do a good job, but I don't see any reason to fixate on a toroid; an EI can do as well or better for filtering.
Another data point to consider:
Note the graph showing the bandwidths of the various transformers tested and the discussion that follows.
1+ ptss, Equi-Tech uses a balanced topology with their transformers so they cancel noise, any noise just like a balanced pre amp circuit. I use a 1.5 RQ on my low level and digital stuff and it is faultless. It will also last longer than I will. They do make them much larger for amplifiers but it gets expensive and IMHO power amps are less sensitive to line garbage. My opinion here is colored as the electrical company forced me into paying for my own line transformer because of my work shop when I built this house. They did not want me dimming everyone else's lights. So, I probably have less garbage to begin with. I do think the 1.5 RQ made a difference sonically but it is a subtle one. For computer audio it is a must.
I use an Apple Mini with a 6 TB hard drive run by Pure Music and it use to crash every two to three hours or so. Now it might crash once a week. That is a big difference and when I unplug it from the 1.5 RQ it goes right back to crashing every two hours. Go figure.
Since the OP was looking in the used category for a product, I would cast my vote for BPT . Not only does it use the transformer type that he requested, it also renders a balanced output . In addition, my model has separate shielding for each secondary winding . The end result is the best isolation for each outlet connected to its own secondary . BPT had many options for upgrades as well, but the model that I own (I believe that it is a BPT 13.5? sorry, too many years ago, and the back is impossible to read given its physical location . The damned thing weighs in at 80 lbs.) I remember that it will support a total of 10 amps total, but EACH winding is rated at 10 Amps as well . I know, everybody wants to say that their product is 'built like a tank', but weight alone is not the justifier here . Truly, from the chassis to the individual components chosen, the BPT brad is like few other products that I have ever owned in terms of quality performance and heavy duty plus build .