Here is a good website to find the addresses of violin makers in Cremona:
http://www.cremonaliuteria.it/indexeng.phpThis association (Consorzio Liutai di Cremona) even has a demo shop with a few instruments from different makers on display and for sale. It is quite nice to see if you get the chance to go there. I also sell good books.
Indeed, when I was there last year, I also thought I would be seeing violin shops all along the streets. Most people work from home. I can understand that perspective, as Cremona is so touristy that they would not get any work done at all if they all had an on-street shop front!
If you can visit the Stradivarius museum, it is very impressive. Or even the violin school. I got a private tour by one of the teachers (we were doing a staff exchange with Cremona at the time) and I was amazed how big it is!
hmmm.... chocolate....