A lot of people i know drink beer..:winkAgree - A soft thin aluminum shim would probably be the best. That's not a common item that most people have access to.
Not sure but a couple layers of aluminum tape just be be the trick? Never tried that one.
Surfacing the brake disc with a 120 grit flapper disc in a orbital grinder works in a pinch if a lathe is not available.
Its an old trick ive heard of and tried, didnt fix my squeal at the time, only improved it a bit, had to chamfer the edge of the brake pad facing the rotation to make it go away completely.