To me the original sights look like they were either set into a flat or dovetail, affixed via braze or solder, and then milled or filed down to match the radius of the barrel.  I was thinking this also could be done  with the Criterion barrel and SS front sight.  However I have never held either part in my hand so I couldn't say for sure.

Now here's a possible stupid question.  Are there any "industrial strength" adhesives out there that could do the job?  After all, it isn't your dad's Elmer's glue anymore.