Best is for you to bring all your gears to the shop and try it out. Some like to pack their bag tight and some prefer to have a bit more room for future expansion. You can never tell such things from a forum's recommendation. If you just want a decent, reasonable priced camera bag, perhaps you can try Lowepro which is everywhere. All camera shops plus places like Challenger carry them...
how much is your "bargain"?
Cathay Photo has a nice collection of bags. You can go there and take a look.
If you want those really bargain type of bags, you can try getting 2nd hand ones in B&S.
Alternatively you can also look at some brands carried by NTUC.
Most camera shops carry camera bags. You can get either a backpack or sling bag, etc. The best is to make your way to these shops and ask (need not bring your gears along becos by stating your requirement, the sales person shall be able to advise). Lowepro is one of the popular brands.