Every last Sunday of the month in Piazzola sul Brenta (Padova) there is a Flee Market in the main square in front of the Villa Contarini. There are over 800 vendors of absolutely anything: you name it. It is quite interesting and amusing, and you may be lucky enough to find exactly that "thing" you were looking for.

You can find some more information about it here - http://www.magicoveneto.it/padovano/piazzola/Mercatino-Antiquariato-Piazzola-sul-Brenta.htm -but it is in Italian.

Here there is more about Flee Markets in the Veneto region - http://www.initaly.com/regions/veneto/markets.htm