Well, I think you can get them in almost any outdoor gear shops. There are a few shops in Queensway Shopping Center. There's one shop in Beach Road, same building as Prince Cinema. Others I can think of would be those bag shops in Heartland shopping centres like Westmall, Lot 1, Jurong Point, etc.
You get the price from normal retail outlets, go to army market and bargain for a lesser price lah.....
As for concern bout fakes and real stuff....normally a fake can be easily spotted by the sewing standards, the workmanship(check the real stuff...see their workmanship).......if not ur eyes really paste stamps liao. haaaaa
If you are really keen on something, you got to put in effort and research to get what you really want. I got two of my deuter bags from army market, im still using them after more than 4 years)