Try the Presto music site in the U.K. They ship around the world and frequently offer significant discounts. You can search by format, such as SACD. Berkshire Record Outlet is another site that sells excess inventory from around the world.
If you use Amazon, it helps to know exactly what you are looking for, and they don’t always clearly identify everything as SACD.
“Popular Classical Music “ is a bit oxymoronic of a term, but let me recommend Beethoven’s Nine Symphonies on the Alia Vox label with Jordi Savall conducting. Savall also made a great recording of Bach’s Brandenburg Concertos. There was a pretty good Planets on the Naxos label a few years back. The labels BIS and Pentatone have large catalogs with lots of Classical Standards included