I am looking for system cable for TC-EX66 & CDP-EX77 & ST-EX77. Any idea where to get it?

Solution
If you mean a ribbon cable that connect the components it would be a proprietary Sony cable that only they might have.
You could download the service manuals and modify the units if you are handy that way.
http://freeservicemanuals.info/en/servicemanuals/viewmanual/Sony/STEX77/