Well, You could do a Google Maps search.
Aside from that, my suggestion is the open field where the IR is being built. That field was quite crowded during National Day last year because it's the closest you can get to Marina Bay [and also the Ben Sheares Bridge]. Just get a long-zoom lens.
Other suggestions: Merlion Walk, outside Esplanade [bad idea, since blocked by Floating Platform], Fullerton Bridge, Water taxi [if you are willing.].
You could also get on the bridge itself by going up some stairs, located near Millenia Walk. Kinda hard to describe to you, but just cross the road after leaving Millenia Walk towards the bridge / road junction. it should be a bit visible.
Benjamin Sheares Bridge is going to get a bit harder to shoot [nicely] due to the constructions around, so all the best!