Did you find an alternate source for your Chromega D gears? I checked into several companies (online) that advertised custom gear fabrication, but the prices were through the roof.
I was wary of replacing the nylon gears on my E-5 with metal gears, suspecting that the toothed flange on the enlarger column might wear rapidly - it's aluminum. But such wear might occur over an irrelevant time frame.
At the top of my list now is starting on 3D printing gears, but since my enlarger is still working, that project doesn't have the urgency others do. I signed up for KHB's email notification for new stock on those gears, but nothing so far. No reply from KHB on the occasions I've asked when the gears might come back into stock.