Protolabs offers cnc turning but the aspect ratio of the plate could make it weird for lathing. FYI protolabs also machined the bottom plate Adele used for the white dewar which worked fine, even though I messed up the finish and had them bead-blast it. Still pumped below 1e-5 torr without problems within a few hours. There's also plenty of sand paper left from her polishing the heat switch parts from grit 280 or so all the way up to 2000 if you want to give polishing it yourself a shot (obviously only for exposed areas, won't work in grooves)