I noticed the encoder wheel on my ACE pro was a bit misaligned and wobbling on the shaft, so I modeled a replica and printed it, and it seems to be holding up well. 

Printing notes: 

I would recommend printing it in the orientation shown in the 2nd picture, to protect the fragile thin wall with the encoder slits during support removal. 

If you can, use a creep-resistant, rigid filament (I chose PETG-CF). Avoid PLA for long term usage because it could creep under the tension of the screw.