Quickest way to get singapore-specific info is probably to talk with whoever you got the boat from. Paddles: all the big manufacturers have online presence, for instance epic, and will ship.
To find SS paddlers near you, do what will probably work everywhere in the world: Follow the throngs of people driving to the beach with stand up boards on their roof racks, then at the put-in, look around for a surfski- if you don't see one then look for a middle aged guy wearing a floppy hat and ask him.
Only half joking... good luck!
