The complete recordings of the Amar-Hindemith quartet are available in a 2 CD set and not particularly expensive:
https://www.discogs.com/release/17898544-Amar-Hindemith-Quartet-Mozart-Beethoven-Dvořák-Verdi-Reger-Hindemith-Bartók-Křenek-Stravinsky-Co
Audio quality is "rough", but I grew up on Bird bootlegs, so hey...
What's striking, to refer to other reviews, is how direct this playing is. There's a lot to be said for that in these pieces! I don't know that anybody today would do it like this.