As someone very familiar with knives and their applications, let me add this.

If you are pushing so hard that the scales break or the glue gives way then either your knife isn't sharp enough or you have the wrong knife for the job. It's sort of like complaining that you broke your finishing hammer while driving framing nails. Right tool, right job.

The sgian Du is a small bladed utility knife, it should be used for small jobs. Cutting small cross section materials of sufficiently soft nature, light carving, cutting string, boxes, etc...

When force does need to be applied, it should be directly to the blade back. If you can't because the blade is sunk too deeply in the material then again, you have the wrong tool for the job.

All that being said I think epoxy, a couple pins, and an end cap should give you all the strength you'll need. The pins can be a decorative addition as well, and the end cap (rather than a bolster) will give strength and provide ornamentation.