I can't imagine any method that would attach those two pieces back together once they are separated.
You could try, very carefully try, super glue around the strap of the outer piece and lay the inner one in and hope that you don't #1, stick your fingers to it and #2 that it sticks together again.
There's just not much surface area left to work with once you remove the throw away part. That edge part is quite thin. Not much to attach to.