I just happened to see these shoes online and I must say...next time I go to Venice I want a pair of them! I have no idea how much they cost. The only thing I know is that they are on sale in a shop close to Ponte Rialto called Pied a Terre, which - by the way- has a website
In the past they were used by gondolieri, but they are becoming trendy among "common" people (although still not so trendy, this is why I like them).
Well, if you go to Venice, maybe you could have a look (no online sale available unfortunately)