I also ordered a pair of the "black plates" from your recommended source. I am okay with hoarding tubes since I believe this Sachs is a keeper. Mated with my Coda 8, I am very happy. I also ordered a bunch or rectifier tubes including a rare 5852 Bendix.
I have a box of 6SN7's from my days with a Dude but those tubes are not as musical as these globed tubes available these days.