Vintage Synth Repair

This is kind of more of an external hardware search than an internal  
one, so I hope it isn't too off the subject.

I'm looking for rackmount ears for my Roland MKS-7.  Not exactly an  
easy thing to find it seems.  The roland site doesn't seem to have  
anything.  Can you suggest some sort of old synth part clearinghouse...?

Thanks,
Paul