Unless you fancy a major design project I think you are screwed. Your best bet is probably to find a second hand module. Even a broken one, provided the display works, would be OK. There are reports of the zebra strip coupling to the LCD being a reliability issue so if the unit is scrap anyway then it may be worthwhile opening it up to see if that is the problem. Be aware that the reports I found were from people who did that when they had missing display lines and they completely screwed up the display by taking it apart.
The data sheet for the Epson controller is available and like many display drivers is designed to cover a range of display sizes. So, in theory, if you could find a display using the same (or software and hardware compatible) drive chip you would be able to hook it up and the have a usable display. It is also possible that the pixels end up in the wrong place i.e. horizontal or vertical pixel lines don't match up.
You could try Roland, but 10 years ago it was a $175 repair. They may not have displays any more. The Vdrums.com forum may be a better place to ask, if you haven't already.
Keith.