This isn't something that could be caused by a mutation in a single nucleotide or a segment being deleted or inserted, the way normal mutations happen and get passed on. This would be an entirely different set of (mirrored) machinery composing (mirrored) structures from (mirrored) subunits.

Whatever caused life to begin in the first place would maybe be the right place to look to recreate this naturally. If life began again from step 0, but with the opposite chirality, it could then progress forward towards mirrored bacteria.