Vintage Synth Repair

First of all, a big hello to everyone on this board!

I'm currently attempting my first synth restoration; a late version
Arp Odyssey.  So far, I've managed to breathe some life into a very
dead synth.  This is a long shot, but I wondered if anyone had a spare
'A' key (just the plastic part) or knew of anywhere to source one. 
I'm not expecting charity, so I'm happy to pay a reasonable amount for
one.

Many thanks!

Barry