Have you tried Soulseek? They have users that have some HQ MP3s, as well as FLACs and other lossless formats. Sometimes you have to like get them to add you to their private share list, but it’s not that hard. You just ask which album/tracks you need, they’ll either make them publically available or add you to their private share list. They’re not hard asses or anything like that (some might be, but I haven’t run into users like that).

Also, rutracker.org and/or rutracker.ru, they both have a pretty good record of keeping up with releases, especially undergorund stuff (metal, EDM, IDM, etc.).

Don’t know the condition in which DC++ is nowadays, used to be pretty popular for sharing music. Mostly HQ MP3s, but some users also had a lot of lossless music. Worth a shot as well IMO. Signing up for servers can be a PITA though (or at least it used to be).