Adin
I'm not sure if this is what you're looking for or not, and the seller's description is rather vague. They do mention these brushes will fit a Diamond Edition. The Diamond Jubilee and the Marquis/Grand Marquis are all model 1521 so I would think it should fit any of those motors. I'm still hunting, so stay tuned!
[URL unfurl="true"]http://www.ezvacuum.com/electrolux-lux-diamond-plastic-models-motor-carbon-brush-1-pair.html[/URL]