NAPA still has the OD kickdown switch available
https://www.napaonline.com/en/p/ECHOD6284
i would also make sure all wires from battery to relay ans relay to solenoid are 12 gauge wire. too small a wire heats and acts like a resistor, and i have has ODs wired through the ignition switch that had problems energizing, so i always fed my relay with a 30 amp fuse and 30 amp circuit breaker in line directly from the battery.....