Keep in mind that both of the UNICO movies, SEA PRINCE AND THE FIRE CHILD and ANGEL'S EGG have all been recently released on blu-ray in Japan. Not sure if THE MOUSE AND HIS CHILD have been released (or will be), but Sanrio owns it, so there is a good chance it could be released.
You can find a 1080p rip of THE FANTASTIC ADVENTURES OF UNICO, UNICO AND THE ISLAND OF MAGIC and ANGEL's EGG here.