If the device is OK electrically, simply add a piece of thermal conducting voltage isolating material (Mica or silica gum) and continue using as nothing would happen.
The plastic has thickness that will leave a gap and heatsink compound isn't a good enough thermal conductor to transfer the heat. If you can't find a non-ebay replacement, you can use a fine sandpaper (400 grit wet) on a perfectly flat hard surface to sand to see all of the metal.
This search shows positive and negative rectifiers that should be a good sub.
APT30D60BC — Octopart
This search shows positive and negative rectifiers that should be a good sub.
APT30D60BC — Octopart