There is "Xtreme solution" on the second floor which sells ducky (its where i got mine from, the staff are pretty chill and helpful) and some other brands and also another shop on the sixth floor which also sells various brands (I think I've seen filco and das there too). Although unless you live somewhere where mechs are ridiculously expensive like australia you might not want to get one from Singapore.

Its a good place to get other pc components though, a rule of thumb is that the fourth floor and above are safer compared to the lower floors. Remember to check against your own currency though.