That printer was essentially a Seiko colorpainter (Later OKI). I'd be willing to bet that a dealer that services Seiko/OKI would be able to help you with that. It would make sense that it would use Seiko heads and ink delivery system, so there probably still some interchangeable parts with the older Seiko colorpainter printers.
What does your nozzle check look like?
Head alignments done?
Uni- and bidirectional alignments done?
And last but not least, print feed adjust (step adjust) is extremely important for these machines. Has this been done?