I just transplanted all of the guts of the Magnavox monitor into the Performa Plus case. Now I basically have a Performa Plus monitor that takes VGA. The picture is great. It's just a tad fuzzy but the colors are really good.
The Magnavox is model CM9032 194T. The front plastic says, "VGA COLOR MONITOR" with a colorful little emblem. This one was manufactured September 1990. The old Performa Plus guts were manufactured February 1993.
My theory is that for the Performa/Performa Plus displays Apple just went with the lowest bidder who could slap a DB-15 cable on a generic VGA monitor. The monitor displayed at http://upload.wikimedia.org/wikipedia/commons/3/3a/Apple_Performa_Plus_Display.jpg looks different than mine.