If I'm understanding your question correctly, I think you're looking for something like Bandcamp which lets you pay to add music or other audio items to your collection which you can stream or download in high quality formats
For example looked up ‘Nirvana’ and I only see their debut album, Bleach, available.
Still a great suggestion! Maybe I can’t get everything from there, but I can get some!
Requires some setup iirc. It's not ideal at all. It's kind of sad that it's so difficult to get music files these days.