Vintage Synth Repair

So I have an ARP Odyssey mkIII with about ten broken keys thanks to 
that wonderful overhanging key design.  I am having trouble locating 
keys to replace them because they are not like the other pratt-reed 
keys I have seen before with the plastic keytop, metal key bar, but 
are all plastic.  If anyone has any information on which keys I need, 
where to get them, or if anyone has any they could part with I would 
greatly appreciate the info.