I needed a replacement for my KN5000 several years ago. I couldn't find one, and finally found a company that was trying to clone other mfgr's drives. I sent it to them, and they reported back that after hours of testing, it was to propriatary, and gave up.
I hate to discourage you, but it is very specialized, and a substitute looks impossable.
pa4X 76 ,Audya 76,Yamaha S970 , vArranger, Hammond SK1, Ketron SD40, Centerpoint Space Station