Amazon. I listen to lots of of recordings of that sort from that era. By way of example, there's multiple masterings of Artur Schnabel's Beethoven piano sonata cycles, including the latest from Warner Brothers [really good, but it seems like a lot of people really miss the surface noise]. It's not easy to navigate, but if you search in the regular Window for Amazon, you'll find more titles than in the "Amazon Music" window, which tends to reduce options.