Southpaw

Birdshill123,, just go to O'Reilly Auto Parts online and search the p/n 75907 and it will be there. You can online or just pick up locally if you have one nearby your location. 

O'Reilly Auto Parts

Cole Hersee Master Disconnect Switch 75907-BX | O'Reilly Auto Parts (oreillyauto.com)

Google

Amazon.com: Cole Hersee 75907-BX Switch (Rot 2 Position Lever) : Automotive

I just bought these Cole Hersee 75907-BX switches, p/n 75907, at O'Reilly auto parts for 85.00. They are rated for 2000A intermittent and 200A continuous for the large lugs and 20A continuous for she small lugs

I had this same issue on the 06 Signature we just bought. Trouble shot the issue to a ground wire in the master closet that was never attached to ground bar from the factory. When you tested your heater fan in bathroom did you use a temporary 12 volt positive and ground or just a 12 volt wire? You may want to use a volt meter on the positive lead feeding the blower and use another ground to see if you have 12 volts. Another item you may want to check continuity with your volt meter between the negative lead feeding your blower motor and another frame ground, you should have continuity.