I need the selectivity switch knob for an SX 100 MKIB. The skirt has left to right on the skirt.."phono .5 kc 1kc 2kc 3kc 5kc" . The knob is split on my receiver and I need another. Please let me know if you have a parts SX 100and what is available. Please email direct. Thanks and 73, John, K5PGW