I don't know if it still counts as modern, but I have stumbled on some pianos manufactured for left handed people.
Basically, the bass are on the right side of the piano and the treble are on the left side. Some left handed pianists commented how they had to re-learn what they learnt on right handed piano, but were able to progress much faster on the left handed one.
Christopher Seed is an international concert pianist who can play piano both normally and in mirror image. In 1997 he commissioned the Dutch firm Poletti and Tuinman Fortepiano Makers to build the world's first left-handed piano. It is a complete mirror image of a normal piano with the high notes on the left and the low notes on the right. The lid opens the other way as well so Chris performs on the right side of the stage (as seen by the audience) and the pedals are reversed.
There are very few of them, because there aren't much demand for such product according to the manufacturers, although some rare people I could come across on the Internet expressed interested. Most of the contents I could find about it are dating back between 2000 and 2013 mostly.
A few example below; I got the Blüthner pictures from a shop, which I will not disclose to avoid advertising them:
Left handed Blüthner Model A upright, notice how the the keys are backward
Left handed Blüthner Model 4 grand
Qualität in feinsten tönen (Quality in the finest tones)
Der Musik zum Fluss verhelfen (help the music flow)
The "badge" seems to say: Modell Loso für Linkshänder (Loso model for left-handers). Notice how the right most keys are A and A-sharp, rather than B-sharp and C.
Left handed Kawai K2 upright from this article
Also see this screenshot from a Blüthner "News for friend" from March 2009:
The picture says:
Mozart, Beethoven Chopin - Blüthner provides instruments for left-anders
These three famous composers and pianists were left-handed and they possibly might have been even more spectacular if they had had a left-handed piano. For the pianist, Geza Loso, a dream came true. When his fingers glide with ease over the black and white keys of his piano, this is due to the help of Blüthner who built a left-handed piano for the left-handed pianist.
The treble notes are situated on the left-hand side and the bass on the right. Mr. Lozo has transcribed his music for this special keyboard.
Fifteen percent of the population are left-handed. The interest was immense when Blüthner constructed and built the first "left-handed" grand piano. Apparently "left-handers" can play the melodies with more ease on such a piano. Mr. Lozo has a music school where he teaches "left-handers". An upright piano is now being prepared, which will be a world novelty when it is completed.
Further information under www.gezaloso.de.
The information are very scarce though, probably because they weren't so popular, but it sounds like there was something going on a dozen years ago in that area, and I couldn't find anything on the website of the brands themselves.