The Sonus Faber tweeter has a modified face plate, note the truncated cutout, that allows it to be closer to the midbass driver. Sonus Faber may only use the standard Vifa ring radiator tweeter but the cutout and gold phase plug will be difficult to copy. However, there is a chance that the tweeter is highly modified for SF. I suggest contacting Sonus Faber directly (as Ellery911 suggested) or contacting a dealer (as stefan@talentconnecion.co.za). Those two should be able to assist and be very helpful.
Best Regards,
Drbarnum
or
Best Regards,
Drbarnum
or