i just checked out Giant, PageOne, HomeFix but to no avail, probably try more. i googled and found someone saying that they do sell it at random local shops but its so random i dunno where. no worries thanks
thanks all i managed to find some random stall in Raffles place that sells it. The push cart at exchange alley sells corporate gifts but also carry random stuff like these. i just tested it, works pretty well and even semi air tight plastic pockets with thicker plastics, not plastic bags.
it costs $6 fyi and uses only alkaline battery but not my 2700 powerex? oh well as long as it works.