I have a Honeywell Electronic air cleaner that has a pair of now open in both directions Varo H447 7337 diodes in its rectifier circuit. The stated output of the power supply is 8,150 V at 2.1 ma. They are black epoxy cases, about 1 inch long. Is there a replacement? And if so what is it? And can I purchase only 2 or thereabouts.