I just finished this bolt-on sharpening accessory using an Eze-Lap diamond hone.
I used a section of the original handle to create a spacer. The heads of the Chicago screws were turned down and the plastic counterbored so that they would sit flush.
The plate was then attached using Goop adhesive. I suppose epoxy could be used but care would have to be taken not to get any on the sharpening surface, which would clog it.