As CocaCola said, your dual-ganged pot is pretty common.
For trivia, I'll mention that when I actually do need a custom pot, I've had good luck
with Maurey Instrument Corp. 5959 W 115th St Alsip, IL 60803.
They ain't cheap, but they're very high quality.
Also for trivia sake, when I need a replacement transformer, I send the old unknown
transformer to:
Mitchell Electronics Corp. 85 W Grand St. Mount Vernon NY 10552
They disassemble the old Xformer and build me an exact replacement.