Bunn BT10-B silicone washer

I took the top off my coffee maker to clean the hard-water scum inside the reservoir and underneath, and found the black washer was ripped. I'm having a hard time finding a replacement. Since I'm not sure that just any washer will work (considering the heat and water), I don't want to put one from around the house in it. I can, and have, been sent the replacement kit to fix the leak concerning the recall of some Bunn coffee makers; but this black silicone/rubber washer isn't included with the kit. Does anyone know what I'm talking about and how I can find that particular washer?

Thanks for any help offered!