The vintageTEK Museum will send you a similar one, the 311-2047-00, for $15 postpaid in the U.S. This is from the 465B and 468 and is a single-shaft "backlash" version instead of the dual-concentric original but it is electrically identical (5K/50K).
Ignore the other parts. We will ship just the dual pot and the knob.
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Bob Haas
Bob Haas