Fishing is not too great in Singapore, below are the options:
1) Local light/micro jigging - there are some charters plying the southern islands for this style of fishing. The jigs range from 5-20g (micro jigging) to 40 - 100g (light) jigging. You can also do madai and inchiku jigging, also about the same weight range. You can expect the likes of small groupers, parrotfish, diamond/golden trevallies. Nothing major, but could be rather fun on a 10lb setup.
2) Reservoir luring - there are peacock bass and giant snakeheads in the reservoir of Singapore. However, local authorities have severely restricted the areas whereby you are allowed to fish. All fishing is land-based, no boats.
3) Paypond - as fishing is terrible in the natural environment, there are many payponds. The GT pond in Singapore is famous as the GTs there are well-taken care of and have played host to many overseas anglers and tackle manufacturers. The fishes are about 5-10+kg but can be pretty fun for a quick fix. And yes, the fishing is not easy as the GTs have been well acclimatized to lures.
I think shopping is a good idea, Kaiser Pro Shop, Sabre Tackle, Anglers Outfitter, Anglers Hut have a good range of tackle.