"Concert Etudes," by Hans Seeling (Peters Edition).
"Etudes," by Carl Baermann (two books), published in Germany.
"Etudes," by Ruthardt (Peters Edition).
But why not select an easy Etude by Chopin and make a start? The best preparation—if not the Etudes themselves—is Heller's Opus 154.
Etudes For Advanced Players to Work at
What regular technical work would you prescribe for a fairly advanced pianist—one who plays pretty well such things as the Chopin Etudes in C minor, Opus 10, No. 12, and in D flat, Opus 25, No. 8, and the B flat minor prelude?
My advice to advanced players is always that they should construct their technical exercises out of such material as the different places in the pieces at hand furnish. If you should feel the need of Etudes for increasing your endurance and control of protracted difficult passages I suggest that you take up the Etudes by Baermann and those by Kessler. The former are a little easier than the latter.
The Value of Clementi's "Gradus" To-day
My first teacher laid great store by Clementi's "Gradus ad Parnassum," and insisted upon taking every study in it, while my new teacher, with whom I recently started lessons, says that it is "outlived, superannuated." Was my old or my new teacher right?
They were both right; one as a pedagogue, the other as a musician. As you do not mention the reason of your first teacher's insistence, I must assume that he employed the "Gradus" as exercises, pure and simple. It serves this purpose quite well, though even as studies for the applying of technical disciplines they are, on account of their dryness, "outlived," as your new teacher correctly says. Modern writers have produced studies which combine with their technical usefulness greater musical value and attractiveness.