Leica in Milano
I'd suggest to visit Foto Dotti in Modena (see below). I promise you won't regret it. I live in Milano, but that's where I bought most of my Leica's gear. Wide choise of brand new and used Leica products, good prices and, most importantly, a great deal of kindness and competence.
Viale Storchi 281 - 41121 Modena (Mo) Italia
Tel: +39-059-821000 - Fax: +39-059-822087
If, on the contrary, you insist on Milano, try at Centro Foto Cine in Piazza Argentina, but it's a different league: you'd have to place an order there and wait. They have no store stock. Besides, they apply little or no discount on the price list.
Last but not least: stay away from Foto Ottica Cavour in Via Fatebenefratelli !!!