Vintage Synth Repair

I've just acquired a Logan String Melody 1.It seems to be working OK( just a couple of minor probs,dirty pots,keyswitches etc) but it is missing some keys.They are C, C#, D, Eflat and G. Does anyone know where I could get replacements from?Thanks in advance Colin.

Sorry if I've posted this twice but things are a bit hectic at the moment.I've acquired a String melody 1 and everything seems to work apart from a few noisy pots and key contacts.The main problem is its missing 5 actual keys in the bottom octave ( C to Eflat and G ).Does anyone know where I can get replacements/substitutes etc.Regards Colin.