First off, yes there are a lot of cities that embrace this type of art form. Major cities across Canada like Halifax, Toronto and Edmonton hold annual busker festivals. In the U. S. you can find buskers daily in Baltimore, San Francisco and Key West. In all of these venues you must audition or apply to perform. In Europe performers stake their claim to an area and try to perform until they are exhausted and leave. Unfortunately, if you set up on the fly and try to perform in most spots, the constables or coppers may try to run you off. It is a lot of fun though to pick a spot and start performing and gather a crowd that will watch you for 30 minutes and then give you a bunch of money. Diabolos are a great prop to perform with and many acts use them because the high toss is a good way to attract a crowd and can be seen from far away.
Regarding where I find stuff...try the Google News Search gadget and type in busker or street performer or spin top, etc.