I'll be traveling to Rome, Florence, La Spezia, Milan, Venice, and maybe Naples in September/ October.
From my web searching, Rome and Naples would have a larger selection. Of course Milan would most likely be the most expensive. There is a tailor named Luigi Gallo; his website: http://imparali.com/a-tailored-suit-is-made-for-one-person-says-luigi-gallo-an-italian-custom-tailor and http://imparali.com/tag/custom-tailored-suits
A related Wall Street Journal Article:
One thing is for sure, be prepared to put out serious cash.
Hope this helps a bit. about 6 years ago