Dyna-glo rmi-80ngt. cuts off fire no rhyme or...

Question

Have a dyna-glo Model # RMI-80NGT serial # 8NT8 001387 30,000 btus ANSIZ21.112-1996. unvented heater that I use in my family room I thought the Thermo coupler was bad but I can not find anywhere to purchase a replacement I have cleaned it out and removed any carbon build up that may be on it. I do not know where to go from here please help thanks in advaceCora Fanning