Are you in the USA?
I know that Woodstream had some Phrag. kovachii for sale somewhat recently, perhaps you can check with them directly via email? I also know that Springwater (via Ebay) has had some recently, but I couldn't tell you if those plants are of good breeding quality or not.
I was also going to mention Ecuagenera BUT with the exact same warning that you already got: They seem to have a considerable problem with mislabeled Phrags these days so I hesitate to recommend them. If you're very familiar with Phrag. kovachii already, then you'd likely be able to tell upon arrival if the plant was mislabeled based on the foliage. But if you're not super familiar with how it looks vegetatively, I wouldn't risk it given the cost. For a Grande, it would be difficult to tell from foliage alone if the ID was correct, as there are many hybrids that would/could look very similar until they bloom.
I'm prepping to downsize my collection a bit in the spring, and I'll have some smaller sized divisions of my Phrag. Wossner Supergrande available if you're interested. I probably do have an extra Phrag. kovachii division in my tubs somewhere as well, but I'd be hesitant to offer it up because it's from a very old (and super, super crappy quality) clone and it's basically been ignored for the past year if it hasn't kicked the bucket.