@darius I asked this same question here in January, and while I don't want to go down the rabbithole of finding that thread again, here are the bookmarks I kept from it:
us.7digital.com/
store.tidal.com/us/
qobuz.com/us-en/shop
prostudiomasters.com/
hdtracks.com/

I have since used 7digital and been happy with the experience.