LOL. Most of the washers you find are very hard. I don't think the originals are. This is like the difference between soft copper tubing (coiled) that you buy at the parts store and the rigid copper water pipe (similar we used in refrigeration.) The difference is whether it's hard or soft, and with copper, it's easy to change. Just heat it to dull red and let it cool. Copper also work hardens, and it doesn't take much to do so. Just bend it a little bit and it's hard LOL
Google it. There's some videos on this very thing.
I'll keep that in mind if the double washer fails. It stopped the weeping on the banjo fitting but now the proportioning valve is leaking at the sending light pin. Had it apart already cleaned it out , new o-ring still seeping. Looked like it had been taken apart before ,sending unit nut is plastic?