Congratulations, Milly!!
They were all commissioned by Paul Wittgenstein, who lost his right arm in WWI. I could also have added Bortkiewicz, Franz Schmidt and Richard Strauss.
Korngold - Piano Concerto for the left hand, Op. 17, 1923
Hindemith - Klaviermusik mit Orchester, Op. 29, 1923
Martinů - Concertino for piano left hand and chamber orchestra, Op. 173, 1926
Prokofiev - Piano Concerto No. 4 for the left hand, Op. 53, 1931
Ravel - Piano Concerto for the Left Hand in D (1929–1930)
Pretty sure we didn't have this before, Tommo, although someone (and it could well have been your good self) suggested it as an incorrect answer a few weeks ago and I squirrelled it away...