I made my eyeglass repair bit into a standard big big bit by making a mold out of wax and using epoxy putty to make bit. First I made impression top and bottom out of wax with normal big bit and then stuck eyeglass repair bit in middle lined up in wax. Then I took epoxy putty and filled in wax mold and pressed down good and made sure I completed the mold. I allowed to dry five minutes before removing from wax and then I lightly sanded careful you want tight fit around new bit. Next I took my new epoxy bit and placed inside bit holder to make sure perfect fit for big bit and allowed to dry 24 hours. I used normal epoxy I believe plenty of strength but you may want to use kind with metal added for extra strength. Enjoy.
decided to try with 3d printing. 7 minutes to print in 2 orientations, vertical, turned out nfg, and horizonal, which worked ok. what i found was that the mid point needed to be positioned close to one end, maybe it would be better with 2 indents to lock in both sides, but I didn't feel like working on it much more for now. pushing it in took some work, i'd probably adjust clearances if i needed something like this