Water heater pressure switch

I have a power-vented Sears/Kenmore hot water heater (which was apparently manufactured by State Industries). The vent blower motor is controlled by a gas pressure switch, and mine is failing in a way which often leaves the blower on after the burner goes off. I want to replace the pressure switch, but the only way Sears sells the part is as part of a $185 thermostat assembly. Does anyone know where I might be able to look to find a compatible pressure switch as an independent part? (I've tried both State Industries and several of the larger parts stores on the Web with no luck.)
Thanks for any help with this, Terry Baker ( snipped-for-privacy@gmail.com)
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