Hi ,
If you are thinking of getting some computer parts or photography gear, you can head down to Sim Lim Square at Rochor Road.Go to the information counter, and get the printed list of reputable shops in Sim Lim Square , compiled by the Singapore Tourism Board. Know the price of the stuff you wanted to buy, before heading there. And bargain.
For photography gear, you can check out, Alan Photo at ground level. For gear related to dive photography, you can check out ScubaCam at Golden Wall centre, just across the street from Sim Lim Square. Look for David. A very knowledgable and helpful photographer. Housing, dome ports and strobes are at prices cheaper than the States.
For sightseeing, maybe you can head down to nearby Suntec City for the Duck Tour ride. Its a amphibious vehicle that will take you through some land tour around Suntec City and Town area, before heading for the sea. And you will have some boating in local waters. Seeing the Singapore city from another view. After which, you can try to book a Sun Set viewing tour from the Duck Tour Counter. You will be lead to the top of the Suntec City office block at 45 stories, and watch the sun set with the CBD ( Central Business Distict ) backdrop. The Duck Tour Counter is located near to Watson store. Or you can do a google on Singapore Duck Tours.
Cheers, hope you will like the visit to Singapore.