you can find stores that sell stuff like that around beach road, but i know there's one store at the esplanade that sells movie and comic stuff (like LOTR rings and Harry Potter Wands) and i saw a katana selling there last time i went. Also you can try that store...um..Caesar's i think. there's one at Suntec City on the 3rd or 4th floor which sells all sorts of swords. they have Aragorn's sword, katanas, Arwen's sword, all sorts of awesome stuff. claymore swords, conan swords, it's awesome.
also, another road singapore has in case of emergencies is the really wide road leading up to changi airport. the middle is essencially potted vegetation that can be removed, and it's long and straight and when you remove the plants in the middle you'll find the resulting space is really wide because you have wide roads going in both directions now opened up for usage. you'll notice the roads to and from changi airport are really wide, but traffic to and from changi airport isn't THAT high.